Denis Thatcher on Mark Thatcher

The Times has an extract from Ferdinand Mount's memoirs about his time as head of the No 10 policy unit and Mrs Thatcher's speechwriter. The whole thing is worth reading, but this is particularly fine:

My son Harry had briefly taken up autograph-hunting and he worked the room, clocking up the white-faced Whitelaw and Parkinson for starters. Then Harry moved on to get a signature from Denis Thatcher. Would it be all right to ask Mark Thatcher for an autograph, too?

“I wouldn’t bother if I was you,” said Denis: “the boy can scarcely write his own name” – which Harry thought the funniest thing he had ever heard.

Mark's twin is no more complimentary about him.