He is only eight years old, and I am now 87, yet he seemed to understand at some profound level what horrors took place at the camp a century ago. We also visited the Jewish museum, with its secretive door that leads to the architect's simile for a gas chamber; and he walked, with clanking feet, across the hall full of metal faces, each one representing a victim of the Holocaust.
It has been interesting for both Winston and me to compare our experience in Germany to the trip we have just completed to the Guantanamo Bay Museum. Of course, it is easy to get carried away by emotion, and it is an ancient adage - sometimes called the Godwin Rule - that any discussion of history will inevitably veer round to Adolph Hitler, no matter what the topic.
At one level, however notorious the Cuban prison may be, discussing a death camp in the same sentence is hyperbolic: More than 200,000 people passed through Sachsenhausen, of whom 30,000 died. With the Guantanamo Detention Centre, closed now for almost 30 years, the total number of prisoners was never more than 779, of whom nine died in custody.
That said, I imagine that more people have heard of Guantanamo than Sachsenhausen. And Winston has a personal link to both. His great-grandfather - my father - was Jewish, and fought in the Second World War; I - his grandfather, a human rights lawyer before my retirement - spent a total of more than a year of my life in Guantanamo, making 35 visits to the Muslim men I represented there.
So perhaps it is just and reasonable that I should record some of the observations we discussed. Certainly, I want him to learn the lessons of Guantanamo which, though well inside living memory, are all too readily forgotten.
There is something I found almost amusing about our arrival at the Guantanamo Museum. We flew our own air taxi direct to the airport on the Leeward side of what used to be the old US naval base, the same place I landed in a charter plane in November 2004.
As a lawyer, I was classed as "the enemy" of the military mission. I had a military escort everywhere. On that first trip, my escort was a genial, ageing sergeant in the US army, and between visits to the detainees, he described how he dreamed one day of building a holiday resort there rather than a prison. After all, it had a runway long enough for a huge jet of the type they used back in the early 2000s, and lots of concrete cells that could be converted into very secure hotel rooms.
What would he think if he could see it now? At Sachsenhausen, Winston took a photograph of the infamous motif on the gate: Arbeit Macht Frei (Work Sets You Free). Similarly, when we touched down at Guantanamo, I pointed out the sign that greeted me when I arrived more than four decades ago: Honor Bound to Defend Freedom.
It meant very different things to the soldiers, who were being told that holding a few Muslims without a trial was the way to preserve liberty, and to the detainees, who had no freedom to defend. The naval base was fairly free of irony, but I felt that I was one of the few people who really was there to defend freedom - and the principles upon which the US was founded.
One of my enduring memories, though, 42 years after my first visit, was the seeming small-town normality of the Windward Side, with Recreation Road, running past the gridiron pitch, the bowling alley and the golf course, albeit changing name before it reached the prison camp.
It was there that I first had a cup of coffee at the McDonald's, escorted by an army colonel. As we entered, a junior soldier saluted him, and snapped: "Honour Bound, Sir!" The colonel saluted lazily back, and replied, "To defend freedom, soldier." I laughed. I thought this was a joke, performed for my entertainment. They were both taken aback. I soon realised that it was the rule - everyone had to parrot the prison motto when they saluted.
At Sachsenhausen, most of the wooden huts that housed the prisoners have long since rotted away, and are now represented only by an oblong of shingle. Nothing much remains of the original Camp X-Ray either, where the first confused and abused detainees arrived in Guantanamo in January 2002.
All we could find were the concrete slabs that were once surrounded by barbed wire. Kudzu has overgrown the place, reminding me a little of the poem Ozymandias. I was rather pleased to be able to direct the young guide to it, and show her where some of the early iconic pictures were taken, the prisoners in their orange jumpsuits, hooded and shackled.
We took a hover shuttle down to the main prison camp which was, in some ways, just as I remember it. Camps Five and Six were high-security prisons, built to withstand the most imaginative escape attempt - although where could one of my clients have escaped to? On one side, he would have found hundreds of kilometres of the Caribbean sea, and on the other, the second largest landmine field in the world guarding us from the perfidious Castro Communists. One of the Guantanamo mythologies involved the periodical explosions that we would hear at night: The guards had been told these were disgruntled Cubans trying to escape to freedom. More likely, it was an overweight iguana trampling on a detonator.
Thinking of those iguanas, I asked Winston what he thought about laws that protected animals.
"That's good!" he replied in his slightly squeaky voice.
"What would you think of a place where the animals have rights, but the people don't?" I asked him.
"That's crazy, Grandpa!" he said. "Is that Animal Farm or something?" I love this kid, that he knows about George Orwell already. So I told him how one of my clients in Guantanamo Bay, Shaker Aamer, read 1984 and re-read it.
"The object of power is power, the object of torture is torture," I intone, quoting Shaker's favourite line. While the detainees suffered torture on a daily basis in the early weeks and months of their imprisonment, by the time I got in to see them (two-and-a-half-years later, after we won Rasul v Bush at the US Supreme Court), the abuses were not as overt.
Another thing Shaker said, that I recited back to Winston, was that the physical torture was not the worst of it. Rather, it was the day-in-day-out nature of the mistreatment; and the endless degradation, reflected mainly in insults to his religious faith.
In Camp Five, I told Winston about Echo Block, the place where the worst long-term abuses took place. That was where Shaker endured months of solitary confinement.
Back in 2012, I remember Shaker describing the cells kept permanently freezing with airconditioning, with essentially nothing in them but the prisoner. He described to me - and, when I got some of the facts through the censors, I passed it on to the world - how there was a concrete slab for a bed, with no mattress and only the thinnest of sheets; a hole in the ground for a toilet; and water coming directly out of a spigot in the wall. Shaker himself had only shorts and a T-shirt, and had to shiver the days and nights away.
The US spokesman told the world that they did not even use "solitary confinement" as a punishment, implying that Shaker was telling untruths, and they refused to allow me to see Echo Block. Later, I discovered that they had simply redefined what they were doing: they called isolation an SCO, which meant "Single Cell Operation", a euphemism that allowed them to tell bald lies to the media.
And now, here we were, Winston and me, an Echo Block cell in front of us, preserved just as it would have been when Shaker suffered there, albeit with the temperature set at a rather more comfortable level. I asked Winston to use the camera built into his contact lenses to take some pictures and zip them directly to Shaker in London, with a warning message that some unhappy memories might echo back to him.
The next stop on the tour was Camp Seven. This was a novelty for me. I was never allowed there back in the early 2000s. Because I had two passports, one American and one British, I was permitted only a "Secret" clearance, and not a TS-SCI (Top Secret-Sensitive Compartmented Information) one, so I could not go to the prison block where the HVD's (high value detainees) were held.
Back in one of my treasure boxes in Dorset I have the red top of a milk carton from Guantanamo because it has HVD emblazoned on it, though there it was for the elevated vitamin D content. The term itself was both offensive and powerful, and I felt the need to talk about it to Winston.
There were a few people in the prison who bragged that they had done terrible things - even been involved in some way in blowing up a building in New York killing 3,000 people. I explained to Winston that it happened on a day called Nine-Eleven. It was a disgusting offence, murdering so many people, but sadly, the only thing that really set it apart from so many other horrors around the world was that it happened in America, and it was shown live on television.
"Any person who would do such a thing is just mentally ill," I told Winston. When the detainees first came to Guantanamo Bay, I explained, the then-secretary of defence, a man called Donald Rumsfeld, said they were the "worst of the worst" people in the world - the word we used then was "terrorist", which I explained was an emotive term used by people who wanted everyone to ignore facts and automatically condemn someone so labelled. This man Rumsfeld said that every last one of them had been captured committing atrocities in Afghanistan, and not only did they have no human rights, but they could even be subjected to torture (he did not use that word, but employed a euphemism, calling their mistreatment "enhanced interrogation techniques").
"That's a very silly thing to call it!" Winston commented, laughing. I agreed with him, but I told him that he needed to understand that sometimes politicians whip up a frenzy of hatred against people. For him to see it in his own terms, I told him how it was a bit like some of his video games that taught him that all Slimes were evil, and had to be killed.
"But Slimes ARE baddies!" he insisted, in that logic-driven way of his.
I am afraid I wagged my finger at him. "Yes, in your game they are wicked, but they're not real. They are make-believe. And they very much aren't human. Real people are never one thing or the other - all good or all bad." I know Winston. He'll remember that next time I am telling him off, and it will come back to me.
So I continued, explaining to him how we certainly can't accept a politician's word when he says that a swath of people should be locked up because he, Rumsfeld, has decided they are bad. And that is why I had come to Guantanamo Bay to get them a fair trial.
"And you know what?" I demanded. "By the time they closed this place, we had proved that 757 of the people were not the bad guys they said they were. Back home, your little school has 100 people in it. What would you say if someone came from London and said everyone in the school was bad?" "I'd say he was a big, fat liar! There's one or two of them I don't like, but only a few," Winston expostulated. He then added an afterthought: "And like you always say, it's probably mostly their parents' fault." "And you'd be right," I replied. "It'd be the same as finding that there were only three kids who had done something wrong in the whole school, not all 100." Winston wanted to know how come some adults could have made so many mistakes. I explained that some Americans had gone around Afghanistan and Pakistan dropping leaflets promising large amounts of money if people would turn in bad guys. We talked a bit about his pocket money, which was now paid in euros since Britain (thankfully) had rejoined the European Union 12 years ago.
He gets three euros a week. How would he feel, I asked him, if I promised him 5,000 euros, just to tell a fib about someone? At first he said he wouldn't do it - he knows I am not keen on lying. But when I explained how many new games he could get to play on his contact lenses, he soon came around.
He even said he'd lie about his sister. I let that one slide - I've had a sister for 87 years myself.
As we had our lunch, Winston and I did make some direct comparisons between what we saw in Sachsenhausen and Guantanamo. While the Holocaust is virtually always associated with the deranged genocide of people from the Jewish race (which I claim, at least in part, as my own), there were actually many victims, and it is important to remember them all - the Jews, to be sure, but also the Roma, the communists, the homosexuals, everyone the Nazi "master race" chose to despise.
Often forgotten among the victims of Sachsenhausen were the Russian prisoners of war, more than 10,000 of whom were taken into a room under the pretext of a medical examination, and shot in the head through a hole in the wall. My grandson and I had stared, for a while, at the spot where their blood was sluiced down the drain.
After the war, the world clubbed together at the United Nations to enact the Genocide Convention to try to forestall the systematic elimination of religious and social groups in the wake of the war. At the same time, though, we agreed upon the 1949 Geneva Conventions, barring the barbaric treatment of PoWs: movies from the period depict PoWs refusing to answer any question beyond name, rank and serial number.
I am not sure how much Winston took in, but I did tell him how the United States and other countries tried to row back from the Geneva Conventions to place those they labelled "terrorists" beyond the reach of the law.
First, someone called President Bush argued that they could be held without legal rights; they could be interrogated for "intelligence"; they could even be tortured in ways that were medieval.
Winston knows a thing or two about the Spanish Inquisition: a couple of years back, I brought it up at the dinner table. Since then, he has periodically accused me of being an Inquisitor when I asked him not to use bad words quite so much.
So I told him about my hobby from way back then in Guantanamo, where I took the dreadful things that we, as Americans, did to the detainees, and matched them with various nightmares from the past. For example, when we hung prisoners up by their wrists, we were emulating what the Inquisition called strappado - I was very proud when the New York Times started to use that term.
But the best example was waterboarding, which the US military described back then as nothing more than an EHT (or Enhanced Interrogation Technique). I explained to Winston that the Inquisition had been honest, 500 years ago, when they called it tortura del agua. But, paradoxically, the Nazis had called it Verscharfte Vernehmung, which translates loosely as "Enhanced Interrogation".
For a while I had feared that the UN Convention Against Torture was in jeopardy as the US tried to justify abhorrent techniques. Indeed, the Guantanamo experiment set us back a generation in this regard, and I doubt we are any closer to a consensus today than we were in 2000.
As I explained to Winston, we have to be eternally vigilant when it comes to human rights. Guantanamo was only the beginning of something far worse.
I told Winston that there was a chap called Barack Obama, who became president in 2009 promising all kinds of changes. He said he would close Guantanamo Bay, and stop the torture. But he did little to educate the world as to what had gone on - all the people who had done torture got clean away with it.
I asked Winston how he would feel if older bullies from another school came in and beat him up, along with all his friends, with the teachers looking on. And how he would feel if the teachers said nobody would be told off, and the bigger boys could lie if they wanted to, and just refuse to admit they did it? Winston thought that was pretty silly.
I told him the real world had been even crazier than that. In the case of Guantanamo, the bullies had tortured people on camera - people like Mohammed el Gharani, who was just 14 years old at the time. He's heard me talk about Mohammed many times. The poor kid spent six years in Guantanamo because the Americans couldn't speak Arabic.
They were asking him where he got his zalat from in Pakistan - a word they thought meant "money" in Arabic, but which meant "salad" in Mohammed's dialect. When he listed a number of vegetable stalls in Karachi, they decided he was an al-Qaeda terrorist financier, who must be older than he admitted. (I ought to explain that "al-Qaeda" translates as "The Base", which is just what the American military called Guantanamo. I make that observation merely because it continues to amuse me how people hated each other, and nobody took the time to understand anything.) When the Americans got through torturing people, they were allowed to destroy the film, and when the government did write a report, the CIA torturers were allowed to black out their names, along with anything bad they didn't want to admit to.
That was passed off as the official Senate Torture Report, years ago back in 2015. It's hard to believe that kind of thing happened, but secrecy was the name of the game then. There was another irony. Back in the 2010s, if you were guilty of something in an American prison, you would be given all kinds of help when paroled back into society. With my clients, who were patently innocent of any wrongdoing … they got nothing.
The people I represented were sent to various places without so much as a by-your-leave, and certainly without an apology or any compensation for what they had suffered. They were told just to get on with it. Remarkably, almost all of them did - (as compared with the seven out of 10 people paroled from regular American prisons who committed crimes after their release). This was a tribute to their resilience, and the efforts by my own charity Reprieve to help them back into society.
The problem with fundamentally weak political leaders - more true of left-leaning people than their conservative peers - is that they want to seem tough on the problems of the world. So President Obama, a constitutional law professor, our first African-American president, was the one who did away with detention without trial in Guantanamo, and substituted it with execution without trial - what I dubbed the Drone Age. I'm still slightly smug all these years later that I coined the phrase, but Winston does not know about the Stone Age yet, so he didn't even grin when I said it.
I still find it bizarre to look back over these years and think of President Obama sitting in the White House on what they called "Terror Tuesday", watching a powerpoint display (that was a kind of projection show, haven't seen them for 20 years) with pictures of bearded Muslim men, deciding who should be killed - a little like Nero in the Colosseum, he would do a metaphorical thumbs up or thumbs down. Then they came up with what they called a Disposition Matrix, what anyone else would call a Kill List - a table of people they wanted to be rid of, a trial being something of an inconvenience.
I made that my project after Guantanamo, because however much I disliked detention without trial, the death penalty without trial was much worse. Not since the Borgias had this been so in vogue. Assassination had been considered illegal since 1758, when legal theorist Emmerich de Vattel labelled the practice nothing more nor less than "treacherous murder". But, equally, we had thought the battle against torture won in 2000, but after 9/11 we learned that some people never read history books.
That was a tough battle. I remember one of my old Guantanamo clients, Sami al-Hajj, was on the kill list. Winston has met Sami, so telling Sami's story meant more than some other people. The US government just could not let go, when we got Sami out of Guantanamo, because he went back to Al Jazeera and did more human rights stories.
RELATED: Sami al-Hajj - remembering Guantanamo The new generation thinks the world is coming to an end. My lad Wilfred (Winston's dad) is going on 40 now, and doing human rights work, which makes me proud. He thinks the world has never been so wicked, and I don't like to tell him he's wrong, as I want him to be tireless in what he is doing.
But actually we've come a long way since the early part of the century. As Winston and I stood on Chapman Beach, looking out to sea, I was glad they made a museum out of this prison. I'm glad I came back after all these years. It reminded me how terrible it was - and if I need a reminder, maybe it's time I updated my book on Guantanamo, Bad Men, to make sure everyone is aware of how far we drifted from the path of human rights all those years ago.
The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial policy.