Robert Fisk: What I learned the day I took tea with Ian Blair

Not long after the 34-day Hizbollah-Israel war in 2006 – in which Israel reached its now almost routine scorecard of killing about 1,300 Lebanese, most of them civilians (the Hizbollah killed 130 Israelis, most of them soldiers) – I received a long letter from a man called Blair.

Not Lord Blair of Isfahan (as he now must be called) but Sir Ian Blair, commissioner of the Metropolitan Police, Britain's top cop who was forced to resign by Boris Johnson in one of the more flagrant political misuses of the office of Mayor of London.

I was struck by Blair's letter; first because I'm not in the habit of receiving mail from policemen; second because it was written by hand across four sides of paper. It invited me to drop round to Scotland Yard for "a cup of tea" when I was next in London. This was too good to miss. Blair had been upset by my Saturday column of 12 August 2006. I had been very unfair, he wrote, to his deputy, Paul Stephenson – today, the Commissioner – who had been boasting at a press conference that week about smashing the biggest terrorist ring in the history of terror.

He had – and subsequent trials suggested he was right – stopped multiple bombers from blowing themselves up in airliners over the Atlantic. My problem was that as I watched Stephenson blathering away on the BBC – in a rare hour of electricity at the height of the Lebanon war – there was some real terror being perpetrated by Israel in Beirut (and some smaller terror being perpetrated by the Hizbollah in Israel). I would love frankly, I wrote, to have Paul and his lads out in Lebanon to stop some real-life terror – which might, perhaps, be connected to "terror plots" in Europe – if, of course, they had the spittle for it.

Thus came Blair's letter. But what made it even odder was that when I eventually passed by London, there was no mention of Paul Stephenson. It was as if the matter had quite slipped Blair's mind. He was a cheerful soul – though I drew in my breath with the age-old, "Is it Bob or Robert?" intro – but clearly had other things on his mind. We agreed we would speak off the record, but since Blair has written what his publishers call his "inside story", I see no reason why I shouldn't recall our meeting.

The word torture came up. Blair was chewing over a very serious moral problem. He said he was troubled by acting on intelligence information from Pakistan which may have been obtained by means that the Met would not encourage. Or as he put it delicately about his Pakistani opposite numbers, "they don't always play by Queensberry rules".

Indeed not. The security lads in Lahore, Pindi or Karachi are quite capable of taking out bits of a man's genitals with a razor – or raping their relatives if information is a bit slow in coming – and this even the Met would not permit. (We shall come to a certain Jean Charles de Menezes later.) "I get information," Blair said to me, "and we find the guns in London exactly where the Pakistanis said they would be. So what am I to do? Ignore what I'm told and place the lives of Londoners in danger? No, I have to act on this information."

But does he give information to the Pakistanis, I asked? Blair said he had absolutely no contact with them. But there was a regular meeting, was there not – a unit called the Joint Terrorist Analysis Centre – at which MI5 and MI6 and the Met and GCHQ and Blair himself took part? Was he not giving information to our security services who then handed it over to the Pakistani boys in blue? The Pakistanis would be interested to learn of their usefulness and would surely return to learn a little more from these unfortunate men. Blair seemed to fold into his chair – he squeezed his knees at one point – and then muttered: "I'll have to have a think about that one."

Blair had been Commissioner during the 7/7 bombings of 2005 – the inquest, of course, started this week – and he had some concerns about how young Britons whose families originated in Pakistan were behaving. It wasn't their parents' fault, he said. The older generation came to Britain to work, enjoyed the good pay and living conditions, and were happy to be British. It was the younger generation who grew up in Britain and who then visited their parents' country and subsequently asked themselves what they were doing in Britain.

I think this was a fair bet – nowhere in the world has there been a 60-year old suicide bomber. But again, I could see Blair's problem. He was a diversifier, a liberal – and thus hated by the Daily Mail – and he ended up trying to find out if the diversification of Britain had gone wrong. He got on badly with most newspapers, rowed with his fellow-cops and finally got chopped down by Boris. I thought at our meeting that Blair was – I was going to write "a misunderstood man", but I think he seemed already slightly crushed.

His only attempt at humour was a lovely tale of how Eliza Manningham-Buller, the head of MI5, lost her make-up after the "bomb plot" story when an airport security man chucked it all out in case it contained bomb-making material. It was the only time in her life, M-B told Blair, that "she almost said, 'Do you know who I am?'."

Maybe it was the de Menezes case that had depressed Blair. De Menezes was a totally innocent Brazilian who was shot dead on the Tube by police officers on the grounds that he was a suicide bomber. So as I stood up, I asked Blair: De Menezes? "I think your paper got it right at the time," he said breezily. "Your headline was, 'In the wrong place. At the wrong time.' That's it – and it will happen again!"

Well, thank God it hasn't. But I won't forget that last remark. As John Gordon used to say in the old, old Sunday Express: makes you sit up a bit, doesn't it?