Frank Dobson is expected to stand down from his post as Health Secretary tomorrow and attempt to become London's Mayor as part of a reshuffle of Tony Blair's Cabinet. His departure would mean that the Prime Minister has at least two Cabinet vacancies to fill, and re-opens the possibility that the Northern Ireland Secretary, Mo Mowlam. will be able to make a return to mainland politics.

Downing Street moved yesterday to avoid a repetition of last summer's reshuffle fever when Tony Blair's spokesman made plain that the prime minister would not use the looming shake-up to upstage William Hague's party conference.