Michael Frayn stood for his portrait, he explained yesterday, and found it remarkably tiring.

"People always say you sit for your portrait, but I was standing. Altogether I stood for 24 hours, 12 two-hour sessions - we did have tea breaks, and I must say they were welcome."

Jennifer McRae is the artist whose long skinny portrait of the long skinny author was unveiled yesterday at the National Portrait Gallery, to celebrate his 70th birthday and the opening of his new play, Democracy, last night at the National Theatre.

She knew as soon as he strode into the gallery to meet her that she had to paint him standing, hands in pockets, head slightly back, "surveying with that gentle scrutiny the world around him", she said.

Frayn and his wife Claire Tomalin achieved an unprecedented literary double last year when his novel Spies and her biography of Pepys were both shortlisted for the Whitbread Book of the Year: she won, but he has now beaten her to the walls of the National Portrait Gallery.

She is now working on a biography of Thomas Hardy, he on a film of Spies. It's going to be tricky if the film director doesn't like the screenplay, since Frayn is writing the screenplay himself and the director is his daughter Rebecca.