The Bloody Sunday inquiry which cost nearly £200 million could not have been done "on the cheap", its author Lord Saville has said.
The Law Lord gave evidence to the Northern Ireland Affairs Committee at Westminster, where he also said it was inevitable it took 12 years to piece together the events in Londonderry in 1972.
His historic inquiry was born out of the Northern Ireland peace process and prompted an apology from Prime Minister David Cameron when he said the killings of 14 civil rights marchers by members of the Parachute Regiment were "unjustified and unjustifiable".
Lord Saville said it had been an honour to conduct the probe and that he was duty-bound to ensure the relatives of the dead and the accused soldiers got legal representation given the seriousness of the allegations at the heart of the controversy.
"If you're going to have a thorough, proper, fair inquiry... it is going to cost, necessarily, a large sum of money and take a very long time," he said.
"Simply, because, if you're going to do it properly and fairly, you've got to look in the greatest possible detail at the evidence and other materials that are available, on which you are going to form a view. That is the starting point.
"If you try and do an inquiry on the cheap, or you try and do it quickly, you come seriously unstuck."
In a reference to the previous investigation into the events of Bloody Sunday which infamously cleared the soldiers of blame, he added: "Lord Widgery was asked to do an inquiry very quickly. And, if I may say so, boy, did he come unstuck."
The Saville Inquiry began in 1998 after it was ordered by the then Prime Minister Tony Blair.
It was the same year that politicians in Northern Ireland negotiated the Good Friday peace agreement and the then Labour Prime Minister agreed to call the inquiry in a bid to heal one of the running sores of the Troubles.