The Duke and Duchess of Cambridge have described their visit to a Nazi concentration camp in Poland as "shattering", and said the site is a "terrible reminder of the cost of war".
Kate and William visited the former Stutthof camp in northern Poland where 65,000 people died during Germany's occupation in the Second World War from disease, malnutrition, physical exhaustion, exposure to the harsh climate and abuse from guards - as well as in the gas chamber used to murder those too sick to work, opposite a brick crematorium.
Both bowed their heads as they were shown inside the room today, which was used to burn the bodies of thousands of victims and Prince William - who was visibly moved - was overheard apologising to the museum director for asking 'so many questions' as they exited they crematorium.
Surrounded by a wire fence and watchtowers, the stark wooden barrack blocks that housed inmates in cramped conditions still stand while personal possessions, from combs and children's dolls have been turned into exhibits in memory of those who perished at the camp almost seven decades ago, alongside portraits drawn by artists incarcerated during the Holocaust.
The royals were shown discarded shoes and clothing seized from prisoners on arrival at the camp and the impact of the visit was clear from the heartfelt message the couple left in the visitors' book before leaving.
"This shattering visit has reminded us of the horrendous murder of six million Jews, drawn from across the whole of Europe, who died in the abominable Holocaust," they wrote. "All of us have an overwhelming responsibility to make sure that we learn the lessons and that the horror of what happened is never forgotten and never repeated."
After a guided tour of the camp, 20 miles from Gdansk, they had an emotional meeting with two British survivors of Stuttoff, Zigi Shipper and Manfred Goldberg, both 87, who were both making their first return to the camp since moving to Britain after the war.
Shipper said William and Kate - who declared they were "honoured" to have met the pair - were clearly "very moved" by what they saw, adding: "You could see their faces. They were in pain."
The friends were liberated in May 1945 by British tanks surrounding the barge on which he was about to be loaded. It was set to be towed out to sea and then blown up with Jews packed into it.
He has returned to Auschwitz-Birkenau several times, where he was also held, but "most probably" wouldn't have come back to Stutthof if it wasn't for the royal visit.
He said: "I asked myself many times 'why don't I want to go to Stutthof?'. I don't know. But when I came I realised how important it was."
Zigi said that when he was a prisoner in the camp he was doing "nothing, no work at all".
He added: "We were just trying to keep warm, huddled together. Then after a while the inside people would go out so the outside people could get warm."
He said about the royal visit: "When a royal goes and it's put on the television or in the paper, people say 'why don't we go?'. And that's what we want.
"People should know that it wasn't just Auschwitch-Birkenau, it wasn't just Bergen-Belsen, look at all the other camps."
The royal couple paid their respects by placing stones by the camps' Jewish memorial, accompanied by Shipper and Goldberg, who recited the El Maleh Rachamim, the Jewish memorial prayer for those who have died.
Placing of stones at a grave or memorial is an old Jewish custom which honours the dead by letting people know that the gravesite has recently been visited.
Shipper was first sent to Auschwitz-Birkenau, before being transported to Stutthof.
Without any family, he said it was only his friends who kept him going.
He said: "I thought the freezing weather there would kill me, especially wearing only the flimsy stripped pyjamas.
"But when they asked volunteers for labour on the railway, I was one of the 20 boys who was picked. I went to Stolp and that's where I met Manfred and his mother."
Goldberg said: "During the Holocaust, Jewish lives did not count. It wasn't in our power to do anything to survive.
"We were on a starvation diet, and to receive our minimal rations we had to give our number - even our names had been taken. I still clearly remember mine, I was 56478.
'But throughout it all, I never lost my determination to survive."
The camp started as an interment centre for Poles after the Nazi invasion in 1939 but became an extermination centre for the whole of Northern Europe.
Enlarged gas ovens were installed as it became part of the Nazi's scheme for the 'Final Solution'.
Around 110,000 people, men, women and children, from 28 countries were imprisoned in Stutthof, where as many as 65,000, including 28,000 members of the Jewish community died.
It was one of the last camps liberated by the Allies in May 1945 Karen Pollock, Chief Executive of the Holocaust Educational Trust which helped arrange the visit, said it sent a "powerful example" to the world about the importance of remembering the horrors the Holocaust.
She said: "I have no doubt that this visit will leave an indelible mark - and meeting Zigi and Manfred, who endured such unimaginable horrors and had the strength and courage to return here today - is a moment they will never forget."
William this week paid tribute to the 'bravery' of the Poles during the brutal Nazi occupation.
Earlier this morning, Kate was all smiles today as she stepped out to begin the next leg of the visit with her husband Prince William.
The Duchess looked radiant in a white floral two-piece from Erdem as she left a building in Warsaw to make the journey to Gdansk, a short flight of just under an hour.
Later the Duke and Duchess will also visit the site of Gdansk's shipyards, the birthplace of Poland's Solidarity movement that helped topple Communist rule.
Here they will meet founding members of the organisation including Lech Walesa, Poland's former president and leader of its peaceful pro-democracy struggle.
In Gdansk's central market square William and Kate will join a street party where they will be offered Goldwasser - a Gdansk liqueur, and traditional Polish pierogi dumplings, while watching amber craftsmen at work, and listening to local musicians and artists.
The royal couple will also visit the Gdansk Shakespeare theatre, which has the Prince of Wales as Patron.
It all seemed to be a bit much for shy Prince George, three, who had to be coaxed off the plane by his father, but confident little sister Charlotte, two, was a natural - waving to onlookers and even shaking hands.
The couple then joined President Andrzej Duda and his wife Agata for lunch before a visit to the 1944 Warsaw Uprising Museum, dedicated to the uprising of 1944 which saw the Polish resistance Home Army attempt to liberate Warsaw from German occupation.
They also tried on VR headsets during an event for start-up businesses at Warsaw's Spire Building. Before taking their leave, the Duke and Duchess spent time with six Polish students who are studying in the U.K.
Later the pair rubbed shoulders with stars including model Joanna Krupa at a garden party where the Duchess wore a dress with a plunging neckline by Polish designer Gosia Baczynska - dubbed the "tsarina of the Polish fashion scene".
The party, in honour of the Queen's birthday, was held at the Orangery in picturesque Łazienki Park.
Chancellor Angela Merkel will hold a private meeting with the royal couple in Berlin at the start of the German leg of their tour on Wednesday, and afterwards William and Kate will visit the Brandenburg Gate, a symbol of German unification.
The mood will change when the Duke and Duchess renew their friendly sporting rivalry, that seems to play a part in most of their trips, when they visit the picturesque Germany city of Heidelberg, twinned with Cambridge.
William and Kate will take to the waters of the River Neckar to cox opposing rowing teams in a race with crews from drawn from Cambridge and Heidelberg.