Today I made my parents proud and was the first member of my family to enter Number 10, Downing Street, Whitehall, London SW1A 2AA. It's all to do with this charity, PiggyBank Kids, which was founded by Sarah Brown before she was the Prime Minister Gordon Brown's wife (she was just the Chancellor Gordon Brown's wife then). Now she is the Prime Minister's wife, so she can hold a reception at Number 10, which you have to assume is better than Number 11. Ironically, she is the President of PiggyBank Kids, which is better than a Prime Minister and presumably what Gordon Brown and that other bloke who was in before him secretly want to be. (In actual fact, what I found out when I was actually inside 10 Downing Street is that Sarah had to ask the Cabinet Secretary if she was allowed to hold an event for her own charity at Number 10, and he said, "Once.")

Last year, I was invited to contribute to a book the charity is putting together called Dads. It's out in time for Father's Day this year, and is full of people writing about dads. The charity is all about helping kids, whether they are born premature or grow up with learning difficulties, that sort of thing, hence the emphasis on parents. (They put out a book called Mums: A Celebration Of Motherhood last year, which comprised short stories. It's just out in paperback and you can buy it for Mother's Day and one pound goes to the charity.) I assume I was asked to write something for the book because it is published by Ebury, who publish my books, and because I wrote a book that was essentially about my mum and dad.

Since this was a non-party political event, and Gordon Brown wouldn't be there, I decided it was ideologically sound to get really excited! We arrived at the big iron gates at just after the 6pm start time and did as instructed, showing our invites to the policeman, who had a clipboard with names on it, just like the doorman at a club or launch party. Joanna Lumley was in front of us, which boded well for the guest list. It's weird, after the security search in a little hut, to suddenly find yourself walking up Downing Street. (When I first came to London, as a boy, you could walk up Downing Street and lots of people did, but in 1989 Mrs Thatcher had the barrier installed to protect her from the IRA. It was a bit English and quaint that the leader of the country just lived in a house without even a front garden to protect them from the outside world.) It was dark, and there was no press corps, so it was really quiet. All of a sudden, we were at the door of Number 10, and being welcomed inside. Past the temporary cloakroom on the right, down the corridor, at each stage pointed in the right direction by ushers, pale yellow wallpaper, lots of gilt edged moulding and pillars, paintings everywhere, and then, turn right and you're walking up the famous staircase, with all the portraits of all the prime ministers. (I started recognising them at Gladstone and paid closer attention after Campbell-Bannerman, and yes, there's the photo of Tony Blair at the top. I'm glad he doesn't live here any more. I met him when he was leader of the opposition at the Q Awards and shook his hand and that was the best time to do so, I think.) Top of the stairs, turn left and you're ushered into the first of three state rooms where the reception takes place. I expect this is where Noel Gallagher shook Tony Blair's hand in the famous photograph.

Drinks proffered on silver trays included an excellent selection of red, white and rose wine, champagne, orange juice and - a nice touch (Joanna Lumley had one) - elderflower cordial. Now, we're looking at about 200 people all spread out over three rooms in a slightly worn Regency style, a huge percentage of them very famous, so the skill was to find a vantage point, look like you have every right to be there (which was, improbably, the case) and star-spot without looking like you're star-spotting. Look, there's Sir Robert Winston chatting to Martha Kearney from The World At One and Newsnight Review. And Anna Ford's just joined them! Wow, hasn't Melvyn Bragg's hair grown? And is he going to speak to anyone all night apart from Fay Weldon?

Sarah Brown appeared at around 6.20 and I would say "worked the room", but she didn't really. She looked relaxed and very attractive in red (I'd say the most attractive prime minister's wife ever - they should put pictures of the prime minister's wives - and one husband - on the wall of a different staircase), and spoke to people she knew, but it wasn't one of those events where, like the Queen, all the guests are "presented" to her for a few meaningless words. So, no, I didn't meet Sarah Brown, but I felt happy to be in her charitable and motherly presence and the short speech she gave about the charity was informative and inclusive. Most of the celebs there had contributed to one of the two books, or were connected to the charity. I like the fact that no photographs were taken. It's not going to be in OK! next week (which is the reason why most people turn out for charity bashes) and yet, it would knock the other events in their "court circular"-type section into a cocked hat.

Let's get this over with. The full list of famous people:

[in no particular order]

• Sebastian Coe
• Norman Tebbit
• Joanna Lumley
• Jon Culshaw
• Nigella Lawson (I didn't actually see her, annoyingly, as she came in late, but she was spotted by my companions)
• Kathy Lette
• Anna Ford
• Laurie McMenemy
• John O'Farrell
• Melvyn Bragg
• Fay Weldon
• Michael Simkins (the actor and author whom I happen to know, and was very glad to see)
• Julia Deakin (the actress who played Marsha in Spaced and Jill in I'm Alan Partridge and is in real life Michael's wife)
• Robert Winston
• Gary Rhodes
• Charlie Higson
• Richard Farleigh (off of series three and four of Dragons' Den)
• Peter Bazalgette
• David Putnam
• David Frost
• Davina McCall
• Arabella Weir
• Trevor Beattie
• Martha Kearney
• Ben Elton
• Ronnie Corbett (Ben and Ronnie spent most of the evening together)
• Alastair Campbell
• Piers Morgan
• Fiona Millar
• Michael Cashman (MEP and former EastEnders star)
• Bruce Fogle (I didn't recognise him but Julia did - he's a famous vet who appears on Radio 2, and father of Ben Fogle the TV presenter)
• Jilly Cooper
• Tanya Byron
• Miriam Stoppard

I'm sure there were more famous writers - possibly Mike Gayle and Joanne Harris? - but that's the full list of people we spotted, without looking like we were spotting them. It was nice to chat to the comedians I am acquainted with, Jon Culshaw and Charlie Higson. Charlie had brought along his dad as his guest, because he'd written about him for the Dads book. When he introduced me, I said I suddenly felt bad for not inviting my dad. "And so you should," said Charlie's dad, who seemed a very nice old gent. I made some excuse about my dad being in Northampton, and Charlie's dad said he'd come up from Somerset and that was no excuse. When I first said hello to Jon, I commented that this was a most unusual place for us to bump into each other. "Not for you, obviously," I added, for the benefit of Piers Morgan.

It's a rum old do. Two hours of looking around and having your champagne flute refilled and eating tiny pieces of food like a single chicory leaf with blue cheese on one end and a miniature heart-shaped biscuit with a pea-sized blob of something savoury on it and some glitter (no, really). And I have saved the best bit till last ... Gordon Brown did turn up! He just appeared, quite small and grey, and said hello to a few people he knew. Again, he didn't work the room. It was very informal in that sense. And it was his wife's gig.

Out of there by 8pm, when it finished (although Jon Culshaw said he reckoned he could stay till 8.30 to make up for the fact that he arrived at 6.30). We were keen to get to a pen and piece of paper so we could write down the names of all the guests. I hope I haven't forgotten anybody. I will certainly never forget the weirdest Valentine's Night of my entire life. (Yes, I did go to the loo in 10 Downing Street, in case you're wondering. Michael Cashman gave me copious directions, which was nice. Nothing much to report, but something you have to do.)