A minute’s silence will be held in Warrington to mark the 25th anniversary of an IRA bombing which killed two young boys.
Johnathan Ball, three, and Tim Parry, 12, died and 54 others were hurt when two bombs hidden inside litter bins exploded on 20 March 1993.
The following day the Provisional IRA acknowledged its involvement.
The Princess Royal is due to be amongst those observing the silence at 12:27 GMT, the time the bombs went off.
“It’s crystal clear – a day in my life I will never ever forget,” Colin Parry, father of Tim, said.
He said “Tim died in my arms” five days after the attack on Bridge Street in the town centre, where he had gone to buy a Mother’s Day card.
“I’m mostly all cried out… there are occasions when a piece of music catches you unawares”.
Mr Parry and his wife Wendy established a Foundation for Peace in the names of the two victims.
Former Det Supt Les Lee, who was in charge of the investigation, said “professionally, it was one of the saddest things in my life”.
“The first thing I saw was the remains of a cast iron bin. There were broken windows.
“The place was silent – that’s what struck me as I was walking up Bridge Street… it was just eerie.
“I looked to my left and in the doorway was the body of Johnathan”.
He said “there was a lot of anger, a lot of disgust” but “it was amazing how the town responded”.
“There’s no doubt in my mind that the events of Warrington had a significant impact on what subsequently happened in Northern Ireland.”
Representatives of the British and Irish governments are due to attend the service on Bridge Street later, where wreaths will be laid and choirs will sing in commemoration.