And he urged Tony Blair to set a date for his departure, to end speculation about it and ensure a smooth handover of power to Gordon Brown, the man widely expected to be the next Labour leader.
They said the e-mail stated he had told the police authority of his intention to leave for personal reasons, but he has not set a date for his departure.
Its scheduled departuredate is March 25, and it will splash down in the Pacific with a payload of 2, 300 pounds of equipment and experiment samples from the Space Station.