Ceremonies have taken place across the world to mark Holocaust Memorial Day.

A memorial is being held in London's Guildhall including written testimony from three Holocaust survivors, the late Reform leader Rabbi Hugo Gryn, historian Emanuel Ringelblum and writer Elie Wiesel.

Their stories will be read by Rabbi Gryn’s son David, historian Simon Schama and journalist Jonathan Freedland.

Liliane Umubyeyi, a survivor of the Rwandan genocide, will also speak.

The Chief Rabbi Lord Jonathan Sacks will be the event's main speaker after Prime Minister Gordon Brown was unable to attend the ceremony due to meetings in Northern Ireland.

The Holocaust Memorial Day Trust has created a Twitter page and a Facebook page to increase digital participation in the event and a video, narrated by Harry Potter actor Daniel Radcliffe, has been released on YouTube.

The official event occurs alongside hundreds of community events across the UK

Earlier today Lord Sacks, together with Bergen-Belsen survivor, Mala Tribich, spoke at Gladys Aylward School in Enfield to over 200 students, a visit organised by the Holocaust Educational Trust.

The Chief Rabbi also devoted today’s Radio Four’s ‘Thought For The Day’ to the victims of the Warsaw ghetto.

Carly Whyborn, chief executive of the Holocaust Memorial Trust, commented: "This is a very poignant year. It is one of the very last years that we are going to have Holocaust survivors in the quantity that we do in the UK today."

She added: "We estimate that there are around 5000 survivors left and we really wanted to supply a theme which bought their stories and their experiences to a much wider audience and this is how we came up with our theme – The Legacy of Hope."

A memorial by artist Nicholas Hedges in an Oxford park has been vandalised. He set up hundreds of two ft-high metal stands containing extracts from a diary written by a Polish mayor during the early 1940s.

Mr Hedges said many of the stands have been removed, but added that although it was unfortunate, he had expected it to happen.

A memorial ceremony has also taken place at Auschwitz concentration camp. This year marks 65 years since the liberation of the death camp.

Israeli Premier Benjamin Netanyahu, Polish President Lech Kaczynski and Holocaust survivors gathered at the camp where more than one million people died. Ivan Martynushkin, 86, and Yakov Vinnochenko, 83, two of the camp’s Russian liberators are also scheduled to attend.

A special ceremony was also held in Warsaw yesterday where Israeli Prime Minister Netanyahu gave a speech paying tribute to those who risked their lives to save Jews from the Nazis.

He said: "We encounter the worst evil in the history of mankind together with the greatest courage in the history of humanity. This is not an easy encounter but it gives us hope and direction for our future. May God avenge the victims.”

Israeli President Shimon Peres has given a speech to the German Parliament to mark Holocaust Memorial Day, where he talked about the death of his grandfather and great-uncles at the hands of the Nazis.