Northern Irish First Minister Peter Robinson told the 400 guests at the Northern Ireland HMD commemoration that a visit to Shoah memorial Yad Vashem in Jerusalem had made a lasting impression.
"I am sure I left asking the question that so many others have asked: How could these atrocities have possibly happened?" Deputy First Minister Martin McGuinness was also at the Belfast event, where a remembrance candle was lit by 13-year-old Logan Kerr, who won a poster design competition for schools. Survivor Mala Tribich was the keynote speaker.
Addressing a 500-plus audience at the HMD ceremony at Dublin's Mansion House, Irish President Michael Higgins said the Holocaust was "a huge stain on European history and shows the true evil that can emerge from hatred, prejudice and intolerance".
In Dundee, Lord Provost John Letford hosted the Scottish ceremony at Caird Hall, where the 400 turnout included many Jews from the Glasgow and Edinburgh communities. Former Denmark chief rabbi, Bent Melchior, recalled being a wartime refugee and urged the community to be aware of the plight of current refugees.
Also participating were Holocaust survivor George Brady, his daughter Lara, Japanese educator Fumiko Ishioka and filmmaker Larry Weinstein. Mr Weinstein's film, Inside Hana's Suitcase, documents the story of Mr Brady's sister Hana, who died in Theresienstadt. Ms Ishioka used Hana's suitcase as a motif for a lesson on the personal tragedies of the Holocaust and, based on the story, now teaches children around the world about the perils of intolerance.
Close on 600 people attended the HMD ceremony at Birmingham Town Hall. David Bloom - whose late wife Magda survived Auschwitz - lit a memorial candle and another survivor, Mindu Hornick, recounted her wartime experiences. Ms Hornick and fellow survivors Lia Lesser, Helga Loeb and Ruth Shire also addressed pupils from five local schools at an event hosted by the Birmingham Progressive community.
In Harrogate, 120 people were at the synagogue for an HMD service at which survivor and shul member Arek Hersh was among the speakers, along with Lord Willis, Andrew Jones MP, and Lord Mayor, Councillor Les Ellington.
Lancaster-born artist Catriona Stamp staged an exhibition, (Dis)Placement, at the Duke's Gallery, exploring how surroundings reflect the identity of Jews. There was also a candelit commemoration at Lancaster Town Hall, where Lytham St Anne's College students gave a presentation based on a recent Auschwitz visit.
Brighton's Jubilee Library staged a Wiener Library travelling exhibition: "Never Again? Thinking about the Holocaust". Organiser Diane Coe said the council was "committed to marking HMD as widely as possible".
Sussex University vice-chancellor Professor Michael Farthing welcomed 100 people to its annual HMD event, organised by the Centre for German-Jewish Studies and sponsored by the Association of Jewish Refugees. Marion Blumenthal Lazan travelled from America to speak on "Four Perfect Pebbles - A Holocaust Story". Organiser Diana Franklyn said: "Marion made a big impression on the students. Several said how wonderful she was to have made so much good from such bad things." Eastbourne Orthodox and Progressive congregations joined forces with Eastbourne Cultural Community to organise an HMD ceremony at which Rabbi Harry Jacobi recalled coming to Britain on the Kindertransport.
In Hastings, 170 people attended a commemoration at St Mary-in-the-Castle, arranged by Brian Linke of the Council of Christians and Jews, together with Hastings and District Jewish Society. A film was screened of a visit by local students and MP Amber Rudd to Auschwitz. Seventy people were at the Adur and Worthing HMD event at Adur Civic Centre, Shoreham.
Bournemouth and Poole HMD committee organised a series of events, including, for the first time, a ceremony in Christchurch. Survivor Janine Webber addressed more than 300 students from local schools, as did Arthur Eggerding, whose parents were members of the Dutch Resistance.
Survivor Freddie Knoller spoke to an 80-strong audience at Reading Civic Centre about his experiences during the Shoah. Guests included the Rwandan High Commissioner, Ernest Rwamucyo.
The Museum of Liverpool hosted a joint event with the Association of Jewish Refugees, where speakers included Guido Alis, who escaped to the UK from Czechoslovakia with his family in 1938. Canon Dr Jules Gomes of Liverpool Anglican Cathedral spoke on the King David campus about "the religious basis of the new antisemitism".
In Sheffield, Lord Mayor, Councillor Sylvia Dunkerly and Rabbi Jonathan Golomb opened an HMD Trust exhibition at the Winter Gardens.
In the Norfolk village of Fulmodeston, a service at Christ Church to mark HMD concluded with the planting in the churchyard of an oak sapling grown from an acorn picked up by the congregation's organist during a visit to Auschwitz. More than 200 people attended a Norwich HMD service at the city centre St Peter Mancroft Church.
A remembrance ceremony at Bangor University, held in conjunction with Gwynedd Council, attracted 75 people, including staff, students and local clergy.
Ramsgate marked HMD at a service in Albion Gardens, where a tree and plaque remembering Sir Moses Montefiore was planted in 2001. Officiants included Thanet Reform's Rabbi Cliff Cohen. Chatham Synagogue was filled to overflowing with 150 people for a ceremony involving local pupils and the Medway Youth Parliament.
Exeter City Council and Devon County Council held an exhibition at the Guildhall and survivor Eva Clarke addressed an event at Mint Methodist Church.
Civic dignitaries were at a service at Cheltenham's Council Chamber conducted by Rev Brian Torode of St Stephen's Church and Cheltenham Hebrew congregation chair Michael Webber.
Anita Lasker-Wallfisch told a capacity 200 crowd at Southend Council Chamber about her time in Auschwitz and Bergen-Belsen. Poems were read by Southend and Westcliff Hebrew Congregation cheder pupils Gina Winston and Daniel Rattner.
Havant borough councillor Gerald Shimbart led an HMD service at the local cemetery attended by 60 people. At the Holocaust memorial outside the D-Day Museum in Southsea, around 200 people heard readings by Portsmouth Synagogue's Warren Freedman and South Hants Reform's Dr Stuart Olesker.
Bedfordshire Progressive and Luton Synagogue held a commemoration at Luton Town Hall, where local high school students highlighted the need to challenge bullying, and a charity worker back from Rwanda reflected on reconciliation.
Rabbi Aaron Lipsey and other faith leaders gave a presentation to the 500 people at the Newcastle HMD ceremony about a forthcoming Auschwitz visit.
Local pupils who had been to Auschwitz also featured in the programme.