When I called up Justin Huggler to tell him I was coming to Berlin, he warned me that he now wore a beard. Isn’t that a bit dangerous these days, I asked? “Not like it is where you live,” he said. This was a few days before the bearded Anis Amri drove his truck into the Berlin Christmas market.

“Of course,” Huggler added bleakly, “around here, they used to like moustaches.” Like everything he would say when we covered the Iraq war together, it took a couple of seconds for his humour to rise to the surface. Germany. Moustaches. Hitler. Got it.

Huggler, I should add, can quote the whole of Shakespeare by heart. He denies this – but he’s never failed on a single abstruse quotation from Hamlet to the Isis-like Titus Andronicus to the Sonnets. Better, I used to tell him, than memorising the whole of the Quran. “Not sure you should say that here,” he’d mutter in Baghdad.

A few years ago, Huggler wrote a novel based on his time as a reporter in Iraq. It’s called The Burden of the Desert, about the most stupid book title in the history of the world. But it’s an absolute cracker, a revelation on the cynicism and cowardice of journalists, the immorality of diplomats and the fury of Arabs.

The bodice-ripping is pretty corny, the violence breath-taking. Indeed, the hero-journalist (whom Huggler would like to be, I suspect) has a driver-cum-fixer – clearly recognisable as our real-life driver in Iraq, a courageous guy call Haider al-Safi, who actually gets murdered in the book. Haider forgave Huggler for his “death” because, he told me, he thought the book so outrageously funny and, besides, Huggler brings him back to life at the end. Justin Lazarus Huggler was always a bit like that, making the dead talk.

Berlin Christmas market lorry attack Show all 18 1 /18 Berlin Christmas market lorry attack Berlin Christmas market lorry attack Several people have been killed after a lorry drove into crowds at a Christmas market in Berlin REUTERS/Fabrizio Bensch Berlin Christmas market lorry attack 'At least nine' people have been killed and more than 50 injured. AP Berlin Christmas market lorry attack Emergency Services rush a Berlin market victim to an ambulance Associated Press Berlin Christmas market lorry attack Police cordoned off the square at Kaiser Wilhelm Memorial Church following the incident REUTERS Berlin Christmas market lorry attack Rescue workers inspect the lorry that crashed into a Christmas market close to the Kaiser Wilhelm memorial church in Berlin EPA Berlin Christmas market lorry attack Emergency crews inspect the lorry that ploughed into a Berlin Christmas market, killing at least nine people AFP Berlin Christmas market lorry attack Fire crews attend the scene of the attack AFP/Getty Berlin Christmas market lorry attack Armed police secure the site of a lorry attack at a Christmas market in Berlin REUTERS Berlin Christmas market lorry attack Crushed debris is visible beneath the wheels of the vehicle REUTERS Berlin Christmas market lorry attack An injured man is pushed to an ambulance REUTERS Berlin Christmas market lorry attack Medics attend an injured person after the lorry attack which killed at least nine and injured more than 50 people AFP/Getty Berlin Christmas market lorry attack Firefighters examine the lorry which was rammed into a Berlin Christmas market REUTERS Berlin Christmas market lorry attack A person is carried into an ambulance REUTERS Berlin Christmas market lorry attack View of the lorry that crashed into a Christmas market in Berlin, killing at least nine and injuring at least 50 people AFP/Getty Berlin Christmas market lorry attack Rescue workers push a person on a stretcher to an ambulance Getty Berlin Christmas market lorry attack Firefighters assess the damage after the lorry rammed the Christmas market, killing 'at least nine', and injuring more than 50 people AP Berlin Christmas market lorry attack Firefighters stand beside a toppled Christmas tree at the site of the suspected terrorist attack in a Berlin Christmas market AP Berlin Christmas market lorry attack Damaged stalls at the scene of the incident at a Berlin Christmas market where at least nine people have been killed EPA

In Iraq 11 years ago, he broke the story in The Independent of a 19-year-old Iraqi civilian driven to his death in the Tigris River by five American soldiers. Zeidun Fahdil could not swim, and was drowned. His brother said the soldiers were laughing when they pushed him into the river. His mother even handed Huggler a letter for President Bush. “We found his jacket in the river,” she wrote. “We shall keep it as a souvenir of the justice my son got from the American soldiers.”

Four of the soldiers were charged with manslaughter, assault and other charges. Two received just six months and 45 days in jail; charges were dismissed against the other two.

Now in Berlin as a freelancer, Huggler is almost resigned about the episode. “I was depressed, but not surprised,” he said. “Maybe I’m getting cynical about the failure of armies to bring their own personnel to justice. But we’re right to investigate these things…at least people know what happened; they can’t say they didn’t know…”

I rather think that “justice” is what we – Huggler and all of us journos – try, or should try, to write about in our daily reports. And now here Huggler is, with his wife Anu, living in the capital of a country whose people, just before I was born, committed the most outrageous crimes against humanity in modern history.

In pictures: Families of Iraq War victims react to Chilcot report Show all 10 1 /10 In pictures: Families of Iraq War victims react to Chilcot report In pictures: Families of Iraq War victims react to Chilcot report Relatives and friends of the military personnel who died in Iraq, leave the Queen Elizabeth II Conference Centre PA In pictures: Families of Iraq War victims react to Chilcot report Dawn Holmes, the mother of L Cpl Sarah Holmes who died in Iraq, is consoled by solicitor Matthew Jury as she leaves the Queen Elizabeth II Conference Centre PA In pictures: Families of Iraq War victims react to Chilcot report A family member holding a photograph of Stephen Robert Wright (R), outside the Queen Elizabeth II Conference Centre, after the publication of the Chilcot inquiry into the Iraq War PA In pictures: Families of Iraq War victims react to Chilcot report Families of soldiers killed in the Iraq conflict stand together outside the Queen Elizabeth II conference centre after the outcome of the Chilcot report Getty Images In pictures: Families of Iraq War victims react to Chilcot report Relatives of military personnel killed during the Iraq War talk at a news conference after listening to Sir John Chilcot present The Iraq Inquiry Report at the Queen Elizabeth II Centre in Westminster Getty In pictures: Families of Iraq War victims react to Chilcot report Relatives of military personnel killed during the Iraq War react after listening to Sir John Chilcot presenting The Iraq Inquiry Report at the Queen Elizabeth II Centre in London AP In pictures: Families of Iraq War victims react to Chilcot report Relatives and friends of military personnel killed during the Iraq War attend a news conference after listening to Sir John Chilcot present The Iraq Inquiry Report at the Queen Elizabeth II Centre in Westminster Getty Images In pictures: Families of Iraq War victims react to Chilcot report Family of those who died in Iraq speak to the media as they leave the Queen Elizabeth II Conference Centre in London PA In pictures: Families of Iraq War victims react to Chilcot report Relatives and friends of military personnel killed during the Iraq War attend a news conference after Sir John Chilcot presented The Iraq Inquiry Report at the Queen Elizabeth II Centre in Westminster Getty Images In pictures: Families of Iraq War victims react to Chilcot report Victoria Jones (L), a relative of a British soldier killed in Iraq, holds a copy of The Report of the Iraq Inquiry, by John Chilcot, at the Queen Elizabeth II centre in London Reuters

I thought at first that perhaps Berlin did not haunt him as much as I feared. He insisted that anti-immigrant hatred was not as deep in modern German society as we supposed, and he liked Angela Merkel: she lived in an ordinary apartment with her husband, shopped at her local supermarket, was uninterested in personal publicity. But when he, Anu and my wife and I all drove out to the Wannsee Villa where Hitler’s war criminals planned the industrial side of the Jewish Holocaust in 1942, the mask slipped.

We prowled the rooms of this delightful lakeside SS guest house with its magnificent windows, parquet floor, statues and gardens where Adolf Eichmann, Reinhard Heydrich, Roland Freisler (later president of the Nazi people’s court) and other monsters met to plan the destruction of the 11 million Jews who in 1933 lived in lands which might fall to Germany.

Among the photographs of Eichmann’s minutes of the meeting were the statistics of this monumentally terrible undertaking. Jews in Lithuania: 34,000; in Belgium: 43,000; in Holland: 160,800… Even neutral Ireland was on the list with 4,000. And of course, my eye skidded to the Middle East. In Syria, 22,000 Jews; in Palestine, 230,000; in Egypt 63,000; in Iraq 125,000 (almost twice the number as Greece); in Iran 95,000; Libya 27,000; Tunisia, 88,000; Algeria 117,000; Morocco 180,000; Turkey 81,000.

The Nazis killed well over half the 11 million Jews on their obscene scorecard, and I noticed Huggler roaming the document cabinets, pointing to the signatures. “Heydrich,” he said, stabbing his finger at the name on the bottom of one page. “Goering, Himmler – they’re all there. Everyone gets nailed except Hitler!” Alas, all too true. The biggest Moloch of them all never left his pawprints on a Holocaust document, allowing the denialists to claim he knew not of the fate of a people he had sworn to destroy.

We looked, as we had to look, at the photographs of the deportations, the railheads, the Jews chosen for gas and cremation at the selection ramps in Poland. We were driving back into central Berlin when Huggler broke our silence. “Your capacity to take in the horrors just runs out,” he said. “You have to come back, again and again.”

It was a relief to go to a memento of the Cold War, the Glienicke Bridge outside Wannsee, where spies and prisoners were exchanged in night and fog between the Russians and the Americans in divided Berlin. Remember Russian spy Rudolf Abel (Mark Rylance) and James Donovan (Tom Hanks) in Bridge of Spies? It was filmed right here, on the real Glienicke bridge – with Merkel turning up without warning to watch the drama.

Huggler pointed upstream. “I interviewed a man who’d swum the Tetlow canal over there. Amazing man. Searchlights all over the water looking for him. Then he got attacked – by a swan!”

This was the same reporter I had come across after a series of bombs exploded among the pilgrims to the Shia Muslim Karbala shrine more than a decade earlier. “Incredible. All these bombs going off, right among the people, blowing them to bits,” he told me when he returned to Baghdad. “And the Shias just went on going into and out of the shrine! This was more important to them than the bombs.”

Isis 'does not have the guts' to continue fight for Mosul, claims Iraqi Prime Minister Haider al-Abadi

We ended up, that freezing, snowy Berlin day, at Potsdam, at the Cecilienhof Palace where Truman, Stalin and Churchill (until he lost the 1945 election) met to decide the future of post-war Europe. Stalin’s room is tiny; he slept on a camp bed, that most ruthless and most powerful dictator to survive, who arrived with thousands of Soviet troops to guard him. “Obsessed by security,” Huggler muttered. I could think of an Iraqi dictator with the same problem.

Churchill, whose Potsdam room is still lined with history books, had already sacrificed Poland to Stalin with Trump-like ruthlessness – though with more historical knowledge than the next US president is ever going to possess. The Big Three conference table is still there with its chairs for the advisers and secretaries. Here it was at Potsdam that Truman told Stalin of the atom bomb, and Stalin – whose spies had told him all about it – showed no emotion.

It was snowing again outside, and we crunched back to our car and drove across the Glienicke again from what had been East Berlin a quarter of a century ago. “You can always tell you’re in what was the east because they still have trams,” Huggler observed coldly. “If the Russians had trams, everyone else in Eastern Europe thought they must have trams.”

The next day, I left for Warsaw and changed trains at Frankfurt on the Oder where the Polish border, moved westwards after the war, now keeps Prussia safely out of German control. Of course, the older houses still look German on the other side of the river. “Do you know that it’s illegal to use the word ‘Prussia’ in Germany in any legal sense?” Huggler had asked me.