Former UK Prime Minister David Cameron has spoken of the huge responsibility he felt when delivering his apology for Bloody Sunday.
Mr Cameron said he decided that his remarks, delivered in 2010, needed to be "absolutely direct and clear".
This weekend sees the 50th anniversary of one of the darkest days in Northern Ireland's history, when British soldiers shot dead 13 civil rights protestors in the Bogside area of Derry.
After Lord Saville produced a report in 2010 which stated that none of the casualties were posing a threat or doing anything that would justify their shooting, Mr Cameron apologised in the House of Commons, saying that the killings were "unjustified and unjustifiable".
Speaking about the events of that day, he told the BBC Radio Ulster Talkback programme that the Saville report was one the "most shocking things" he had ever read.
He said: "What I was feeling was what a huge responsibility it was to try and get this right, because the families affected, people in Northern Ireland had been waiting for this for so long."
Mr Cameron continued: "I knew in this case there would be thousands of people listening in Derry wanting to know what Saville had said.
"Ultimately I had come to the conclusion that it needed to be a very clear and frank apology and explanation, and don't try and qualify it in any way.
"The one thing I tried to do was to explain why I felt so shocked by what I had read.
"The shocking nature of what Saville uncovered, I just knew it had to be very clear, very frank and not trying to have it both ways."
Mr Cameron said he was "very moved" when he later saw the scenes in Derry of people welcoming his speech.
Lord Saville told the programme that the question of whether there should be prosecutions for what happened at Bloody Sunday in 1972 remains "difficult".
He said: "I can understand completely the feeling of the families of those who died that they want to see justice done, that is a perfectly reasonable position to take up.
"On the other hand, decades and decades have gone by and it can be said that it is really rather unfair to soldiers to prosecute them after such a long time has gone by."
