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Actually, he slipped past me in the queue at Starbucks at St Pancras railway station. He went straight to a table without buying anything - and that set my sense of fair play twitching.
Turns out a colleague/assistant was doing the queueing for him, which I guess is fair enough?
I sat at the table next to him. At this point I thought he was just some young exec who looked a bit like David Cameron (I'd not met him before).
But when he opened his mouth to talk with said assistant the voice and content of their conversation was a heavy hint.
So I turned to him and asked: "You look familiar. Should I know you?"
He smiled. "Perhaps"
I raised an eyebrow, inviting clarification.
"I'm David Cameron, leader of The Conservative Party."
So. I shook his hand. Wished him luck. But told him I wouldn't be supporting him all the way.
I asked if I could take a snap (to tweet) and also whether he was using Twitter himself.
I told him I'd heard what he'd said about Twitter while being interview by Absolute Radio.
And he explained he didn't use it.
Politicians, he said, needed to think about what they said, before they said it.
He worried that those who tweeted all the time were sharing a stream of consciousness.
I said politicians ought not think too hard before they speak, they should tweet their stream of consciousness. I'd prefer the direct honesty.
And I cited John Prescott (@johnprescott) - and how for years the media had painted him as a bumbling fool - but Twitter enabled him to go direct to the public - to disintermediate the media - revealing the passionate and intelligent man Prescott actually is, rather than the charicature you see in the press.
Cameron did concede that Prescott is a very clever man - but also pointed out that the 140characters of Twitter were a blessed limitation on Prescott's tendency to verbosity. A fair point.
I don't suppose Cameron will start tweeting any time soon. Which is a shame.
Because I prefer my politicians to tell me what they honestly think and as directly as possibly. I want them to admit their human face, warts and all - rather than a mediated, bland/sanitised version of themselves.
Twitter enables that way better than any amount of 'press' ever can.
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I only wish more politicians of all parties would give it a go. We may end up knowing who and what we're expected to vote for. And that would be a pleasant first.
UPDATE: Jonathan Macdonald shared an image that captures me sat on the next table to Cameron - just before I was sure who he was and started bending his ear. Watchers watching the watchers :-) View it larger here.