Appearing on tonight's Parkinson show, the Old Etonian Conservative leader explains how the Croydon-born model thought he was "something to do with drainage" when they met recently.
Mr Cameron told Michael Parkinson he had been a little starstruck. Scrambling for something to say, he recalled that the model had a house in his Oxfordshire constituency.
"We'd had these terrible floods in West Oxfordshire and so I said, 'Very nice to meet you, very sorry about the flooding in your house. I know your local pub has been flooded, I've been to see the publican and I know you like to go to the pub and so I know it's going to reopen in six months,'" he said.
"So I went on like this, twittering on, and she turned around and said, 'God, you sound like a really useful guy, can I have your phone number?'"Returning to his table, he told his fellow dinner guests: "The good news is, I met Kate Moss and she wanted my telephone number. The bad news is, I think she thinks I'm something to do with drainage."