Sir Liam Donaldson, the Government's chief medical officer, will step down next May, it was announced yesterday. He has been in the job since 1998, and had originally intended to leave earlier this year.
Sir Liam has led the Government's swine flu pandemic plans, and has told ministers he will stay on past May should the virus take an unexpected turn for the worse.
Since 1998, Sir Liam has been at the heart of many health issues, including making England smoke-free and creating new laws on the use of stem cells, organs and tissue.
Earlier this year, Sir Liam clashed with the Government over plans to introduce a minimum price on a unit of alcohol. He had favoured setting a price of 50p, but the Prime Minister, Gordon Brown, said he did not want to penalise the majority of sensible drinkers.
In his resignation letter Sir Liam said: "I have been immensely privileged to serve in this post over the past nearly 12 years."