By Jackie Storer
BBC News political reporter
One was a 78-year-old survivor of the Holocaust, in which six million Jews were murdered by the Nazis.
The other was a former far right activist, who used to spread the message that the Holocaust never happened.
Mr Halter says he is working for a harmonious world
But during a short fringe event at the Labour Party conference in Brighton, the two men sat side by side to highlight their belief that hatred can only be defeated by education.
Ex-British National Party member Matthew Collins argued that unless mainstream political parties re-engage with voters, what he described as fascist groups will win council and constituency seats.
Polish-born Roman Halter told his own harrowing tale to warn that genocide on the scale that he and his contemporaries saw must never happen again.
The pair were invited to share their experiences by the Holocaust Educational Trust, a group whose aim is to keep the memory of the atrocities alive by working in schools across the country.
Mr Collins, who is no longer involved with the BNP, is now a director of the campaigning group Operation Wedge, which tries to protect and educate Britain's youth against racism.
He told how he was only 15 when he became involved with the far right, following a meeting in Bromley where a former school teacher addressed the floor to insist that the Holocaust had not happened.
The message was that the Holocaust "was a hoax, that those who claimed to have survived it were part of a huge conspiracy to defraud people", he said.
'Besmirch the memory'
Mr Collins told the meeting: "I did realise at 16 it was important to tell people that the Holocaust didn't happen.
"The BNP will tell you that immigration is as a result of the Jewish domination to bring black people here to enslave white people to keep wages low. They are mad, absolutely mad."
However, commenting later, BNP spokesman Phil Edwards said the party Mr Collins was associated with as a youth "in no way resembles the party of today".
The BNP has some Jewish members, he added, and was "not anti-Semitic and does not discriminate on grounds of religion".
In June 2004's European elections, the BNP polled nearly a million votes - an advance Mr Collins put down to its campaigning strength in areas often neglected by the mainstream parties.
"There are places in this country where the only election material people will see this week will be from the BNP."
He told the Labour fringe meeting: "If you want to keep your seats and your council seats, and make your party stronger, when it comes to fighting fascism, politics is the way. And there's more to fighting fascism than just once every four years in a political leaflet."
Turning to the audience, Mr Collins said: "This Labour Party of yours is not about supping champagne, it's about fighting fascism, it's about reigniting politics, and that's everyone, so do it - soon."
Only minutes earlier, the small packed room in the heart of Brighton's Old Ship Hotel, fell silent when Mr Halter explained how he had been just 12 years old when Hitler's forces entered his home town in north west Poland.
The youngest of seven children, he was on one of the first transports into Lodz ghetto in 1940, and was on one of the last transports out.
By 1942 he had lost all members of his family. In 1944 he was taken to Auschwitz by cattle truck, 80 people squeezed into each one, before moving on to Dresden, which was finally liberated by the Russians.
He told the audience: "A colleague of mine, also a Holocaust survivor no longer alive, said a Holocaust survivor has been a witness who has experienced the genocide, therefore it is his duty to testify.
"It is important as a Holocaust survivor to counsel the young people in schools and towards bringing about a harmoniously better world."
'Evil in us all'
Former Labour minister Stephen Twigg, who lost his seat at the last election, joined the meeting to warn that Labour spent too much energy campaigning in marginal seats.
This meant "that we often neglect the safer more heartland constituencies" - areas often targeted by the BNP, he said.
"If we are going to address some of the real challenges, one of the ways we will certainly do that is through citizenship education in our schools, and as part of that Holocaust education," he said.
Trevor Phillips, chairman of the Commission for Racial Equality, said there was a need to address isolationism in all communities.
It was also necessary to keep alive the memory of the Holocaust to remind people that "evil is not out there, it is in all of us", he said.
"The reason this happens is because we stop thinking of other groups of people as human beings like ourselves. They become easy to demonise," he said.
BNP spokesman Phil Edwards said his party did not have a view on the Holocaust. "It is not part of the BNP to say whether it happened or not," he said.
"We live in a democracy and people are free to have any views they want," he said.
But he added: "There can be no doubt that immigrants from third world countries keep wages low - it's blindingly obvious, isn't it?"