I don't believe it was as clear-cut as has been suggested
Whats not clear to you m8? They asked from Hamilton did he deliberately let Trulli pass, he said no. Radio traffic clearly proves that he did..
So he put the blame on Trulli, instead of admitting he let Trulli by.. pretty clear imo.

Sorry... didn't see this until now. As I said in my post, my instinct was that this sorry affair was initiated by the team, and not by Hamilton. This has been borne out by subsequent developments, and we were treated to the unusual sight of contrition by Hamilton, and dare I suggest humility! The Mclaren official who took the fall was clearly a patsy IMO, and I reckon that the order to deny the conversation came from the very top (Whitmarsh?). I do not consider that Hamilton had any say in the matter, and was simply ordered to sing from the same hymn-sheet.
As for the basis of the decision not to come clean; I cannot understand why they didn't just admit the fact that Hamilton allowed Trulli to re-pass, particularly as he had said as much to the BBC before heading off to the stewards office. Having read the transcript of the conversation, it is clear that there was a discussion as to the legality of the pass; in my opinion, this is due to the problems encountered after Spa last year, and McLaren are perhaps a little paranoid. McLaren stated that they were on the blower to the race director, and that Hamilton should allow Trulli to re-pass, although Hamilton clearly did not agree with this interpretation.
McLaren had a ready-made excuse for slowing to allow Trulli to pass, in that they were unable to obtain a definitive judgement on the legality of the overtake, and therefore wanted to protect their 4th place, with a view to arguing the case after the race. Why they did not argue this in the stewards room is a mystery to me, as if they had, bearing in mind the race effectively finished under the safety car, Hamilton and Trulli's positions could have been reversed, assuming that the stewards accepted Trulli was not given a choice other than to pass Hamilton.
It has not been McLaren's finest hour; however, I would argue that Hamilton's unreserved apology represents the finest off-track moment of his career. I am sure people would argue that he could have blown the whistle, but under pressure form the team, I do not think he had a choice. Let us not forget that, whether we like it or not, cheating is all part of the game of F1, and many times teams and drivers have been found-out. Consider the issue of Ferrari's extending front-wing of a few seasons ago; it had clearly been engineered to extend, totally contrary to the rules. The antics of Schumacher, attempting to drive Villeneuve off track, or blocking the Monaco track at the end of qualifying are just two further examples of teams and drivers trying to cheat an advantage.