"He's a lovely healthy boy, whom we've called Rex Antony Octavian," says her husband, Rodolphe von Hofmannsthal, who owns the fashionable Dicksmith Gallery, in Hoxton.

"He weighed 8lb, 2oz and was born at the University College Hospital. At first, I thought he looked like me, but now I think he looks more of a Snowdon."

Rodolphe, a 27-year-old great-grandson of the poet and dramatist Hugo von Hofmannsthal, librettist to Richard Strauss, married Lady Frances, 28, the only child from Snowdon's second marriage, to the former film assistant Lucy Lindsay-Hogg, in 2006.