The former First Minister and co-architect of the Good Friday Agreement will be laid to rest in Lisburn after a ceremony at Harmony Hill Presbyterian Church.
Tributes to Lord Trimble have continued to flow throughout the week following the announcement on Tuesday of his passing following a short illness.
Irish President Michael D Higgins is to attend and will be joined by Taoiseach Micheál Martin.
Mr Higgins’ attendance will be seen as a conciliatory gesture by unionists following his refusal last year to take up an invitation to attend a church ceremony to mark the 100th anniversary of the creation of the state.
A spokesman for Mr Higgins said he would attend the funeral of Lord Trimble, who was a joint Nobel Prize winner with John Hume of the SDLP for their efforts in the peace process.
They are expected to be joined by a number of Irish government ministers, as well as Tánaiste Leo Varadkar.
Sinn Féin’s First Minister-in-waiting Michelle O’Neill will be there as will party President Mary Lou McDonald.
It is not clear if Gerry Adams, the former West Belfast MP and co-creator of the agreement, will attend. Last week he spoke warmly of Lord Trimble’s role in negotiations, thanking him for contribution and speaking of his “deep regret” at news of his passing.
Former Taoiseach Bertie Ahern, who formed a close bond with the then UUP leader and who was guest at the unveiling of a portrait of Lord Trimble at Queen’s University last month, is out of the country on holiday. But it is understood he is looking at options for him to return for the funeral.
There is expected to be a significant turnout from local political leaders, with DUP chief and former UUP colleague Sir Jeffrey Donaldson, UUP leader Doug Beattie, Naomi Long of the Alliance Party and SDLP boss Colum Eastwood all due in Lisburn today.
Former political allies from the GFA negotiations in 1998 will be there as will one-time political foes and they will be joined by current MLAs.
The outpouring of goodwill toward Lord Trimble has resulted in him achieving a political unity that eluded him 24 years ago.
His death means very few of the chief architects of the peace accord remain with us. Ian Paisley in 2014 and the subsequent passing of Martin McGuinness in 2017 and that of Seamus Mallon in 2020 has stripped Irish politics of many of those who made peace in Northern Ireland.
US Consul in Belfast Paul Narain will represent the US government tomorrow while Secretary of State Shailesh Vara and Shadow Secretary Peter Kyle will also attend.
It is not clear if other key players – former Prime Minister Tony Blair or his special adviser Jonathan Powell – will attend.
Lord Trimble is survived by wife Daphne, children Richard, Victoria, Nicholas and Sarah, and grandchildren Matthew, Anastasia, and Georgia. He will be laid to rest at Blaris Cemetery in Lisburn following the 12.30pm funeral service.