Lady Thatcher has been forced to pull out of a Downing Street party to mark her 85th birthday after being taken ill with flu, Downing Street said today.

The former prime minister had been due to attend a gathering tonight of around 150 friends and former colleagues hosted by David Cameron to mark the birthday.

It will still go ahead at her insistence, No 10 said, with a fresh event to be put on when she has recovered.