Julian Bevan, for the prosecution, said rough, typewritten notes of the interviews with Mr Armstrong, containing amendments and additions, discovered in May 1989, came before the notes of the confessions. 'The notes were manufactured in order to give their evidence credence,' he said.
A detailed comparison showed 'major differences' suggesting 'the typewritten notes must have been made before the handwritten notes ever came into existence.'
The typewritten notes were discovered in files during inquiries by Avon and Somerset police in preparation for the appeal of the Four in October 1989, when they were released.
Thomas Style, 59, a former detective chief inspector, John Donaldson, 57, a former detective sergeant, and Vernon Attwell, 52, a former detective constable, all deny conspiring together between October 1974 and October 1975 to pervert the course of justice.
Mr Bevan said that in 1974 it had not been police practice to record interviews with suspects contemporaneously, but where it occurred, the interviews achieved a higher degree of reliability.
Mr Bevan said Mr Armstrong, then 24, had been arrested by Surrey police along with the three other members of what had become known as the Guildford Four - Paul Hill, Gerald Conlon, both then 20, and Carole Richardson, 17 - for the bombings of public houses in Guildford and Woolwich in autumn 1974.
The following day, Mr Attwell made notes of an interview between the detectives and Mr Armstrong. He named Mr Conlon and Mr Hill as IRA 'lieutenants' and described a trip to Guildford with both of them and Ms Richardson in a car driven by another man, named as Paul Coleman. He said he kept watch while Ms Richardson and Mr Conlon planted a bomb in a public house.
Mr Bevan said during the interview Mr Armstrong was confronted with Mr Coleman but that when the handwritten notes were compared with the typed ones there was a 'complete shift in times and . . . a complete change in what was actually said'.
At the end of the two-and-a-half- hour interrogation, Mr Armstrong signed a statement, which Mr Style wrote out, repeating the substance of the interview. Mr Bevan said the contemporaneous interview and the written statement gave the prosecution 'a very strong case'.
'At the trial . . . these three defendents denied that Armstrong had been hit, reduced to tears, intimidated and that most of these admissions were in response to suggestions. (They) refuted the allegations, saying the handwritten notes were contemporaneously written.'
Mr Bevan added: 'The . . . truth is that these so-called contemporaneous notes were not contemporaneous at all but were compiled after the interview itself. It is the Crown's case that these three defendents lied about the origins of these notes in order to bolster their evidence.'
The following day, when notes were made by Mr Donaldson, Mr Armstrong allegedly made further confessions. He also changed his story to say he had planted the bomb with Ms Richardson.
Mr Bevan said Mr Style was recorded in the contemporaneous notes as leaving the room for 50 minutes but timings in the typewritten notes were different.
After Mr Armstrong was charged, he admitted the bombings during interviews with Scotland Yard officers, including Sir Peter Imbert, former Commissioner of the Metropolitan Police, then a detective superintendent. Mr Armstrong made no complaint about treatment, Mr Bevan said.
The Surrey detectives had suggested the typewritten notes were made after the contemporaneous notes for internal police purposes, with speed paramount over accuracy.
It was said they had then been given to police typists for assistance. Mr Bevan said: 'The crucial question is which came first . . . my submission is that the typed came first.'