Embarrassing, but for whom ... Blair with his then Secretary of State for Northern Ireland Peter Mandelson. Photograph: Paul Faith/PA
The man in front of me looked like a warm-up artist for a Blackpool cabaret act - and frankly I'd never heard of him. But my presenter Andrew Rawnsley assured me that Barry Cox was a highly successful television executive - and one of Tony Blair's oldest mates.
And now, it seemed, Bazza was ready to cough.
We were filming interviews for a ludicrously ambitious series of programmes that aimed to encompass Blair's entire premiership - to distil it into a narrative that was nuanced and detailed, yet also somehow comprehensive.
"Of course Peter Mandelson had an almost homoerotic admiration for Tony - it was embarrassing," opined Bazza in one of his gloriously unguarded off-piste moments.
As the cameras rolled and the film crew's collective jaw hit the floor, I cast a sideways glance at Andrew. Ever the professional, Rawnsley's bulldog chin held firm - but the faintest of twitches at the corners of his mouth told me that, like myself, he was delighted by the uncovering of one more little gem for our final cut.
Not every day was like this. We had interviewed dozens of Westminster's finest, and some had already hit the cutting room floor, undone by their slavish adherence to the party line.
But today was a good day. Barry was off the leash.
"Cherie would get very angry with Gordon's bad behaviour. She would say to Tony: I think you should get rid of him." Blimey. Now he was really warming up. What could he tell us about Alistair Campbell leaving Number 10 - did he jump or was he pushed? "Oh yes, Tony had to chop him off because of the way he was behaving at that point - he did get rid of Alistair, yes." Ooerr. It's revelations like these that make my job worth getting out of bed for, and there are many more in the programmes - not least from Peter Mandelson himself.
I just hope that Barry isn't crossed off any Christmas card lists. Because it was moments of refreshing honesty like his that enabled us to lift our essentially fair-minded series out of the realm of political banality, and into one of high political drama.
And as for working with Andrew "One-Take" Rawnsley? Andrew was a delight - vastly knowledgeable, undeniably talented and unfailingly charming. Except for when he was banging his fists down extremely hard on the meeting room table during scripting sessions, puce with rage and bellowing at me. Very loudly indeed.
All part of the creative process, dahling...
· The Rise and Fall of Tony Blair is on Channel 4 on June 23 & 25
