THE tie! The tie! That was his first mistake. It was a dazzling lime green. On the TV screen it almost strobed. All around him were dark blues and purples: even the press wore the kind of sober ties one might wear to the funeral of a slight acquaintance. Lime green did not suggest contrition. Nor did anything he said.

Bob Diamond faced the UK Treasury select committee for three hours that shed very little light on the arcane matters supposedly under discussion, although a considerable amount on Diamond himself and the bank he had commanded less than 48 hours earlier.

There was no doubt about his view of the behaviour of Barclays' Libor-fixers - "appalling", "reprehensible", "abhorrent", "wrong".

Equally, he had no doubt about his view of the 140086 members of the 141100 staff who he said were not involved. "History will judge Barclays as an incredible institution because of its people," he insisted.

But he had some difficulty remembering that staffing levels had just been reduced: he kept talking about his role in the present tense. "As chief executive I have regular, official meetings." "I am the chief executive today." He seemed in denial, and not just about the things he was trying to deny.

It is easy to criticise the committee for not being forensic enough. The MPs would certainly be far more effective if they offered half a dozen interrogators rather than 13 all adding their several billions' worth. But anyone who has seen a US Senate hearing would recognise that, in comparison, this lot were like a charm of Atticus finches.

Diamond's response would have seemed extraordinary had we not been conditioned by listening to James Murdoch at similar length in a similar accent. Different haircut, same approach. He did not know, he was not told; it was all the fault of a few rogue reporters.

"Why were you unaware?"

"I was not brought to that level."

Asked by the Tory MP David Ruffley for a yes-or-no answer, he offered a thousand words. Asked by the Lib Dem MP John Thurso to say something to small businessmen, he talked about "the people who look after small businesses" in a manner that was not intended to sound dismissive, but did.

Then he went straight on to derivatives. And that, not the Libor rates, sums up the real problem: the general public's near-unanimous sense that their problems are not, to the banks, a big enough deal. Literally.

He also kept first-naming the committee members, which was another tone-deaf strategy.

The public will now be more confused than ever about who said what to whom, when and why. But far more important was the missed opportunity to do something to help the company he claims to love: persuading its customers - and, indeed, its shareholders - that here is an organisation on their side and their wavelength.

In his resignation statement, Diamond said the impression created of Barclays "could not be further from the truth". The implication was that, behind the Bollinger, this was really a company dedicated to helping old ladies cross the road. It did not seem as though Diamond would be spending his increased spare time doing anything like that. But if he does, he will definitely call the ladies by their first names.

© 2012 The Financial Times Limited