Mike's affidavit is certainly not thrown into question if there is even the slightest doubt that it was in Mike's own words and that he was aware of what he was signing. Affidavits or witness statements are frequently drafted by lawyers on the basis of what a witness has told them and it's not impossible that there can be a misunderstanding over a date which is not picked up in the final draft. If Alan Gray took on the same role as a solicitor, the key thing is that the affidavit was based on what Mike had told him, so unless there is an allegation being made that Gray fabricated the affidavit then, even if Mike didn't read it properly before signing it, it still reflects his version of events.
And what I note is that the key point of my post has been totally ignored. That key point is that there are a number of obvious dating errors in Mike's affidavit. I mean, he says he bought his word processor in 1985. Does the fact that this is the wrong year means that he never bought a word processor? Clearly not. But that's the logic being applied to the guardbook. And Mike says he came up with his forgery story in November 1993, which he then changes to December 1993. But that isn't correct. So does that mean he never offered up a forgery story? No, he did but it was in June 1994. He says that Tony died in about May 1990. But he didn't. So does that mean that Tony didn't die? Obviously not. He died in August 1991. Given these errors, the fact that Mike might have got the date wrong about the acquisition of the guardbook is hardly a fatal flaw.