The government's chief medical officer, Sir Liam Donaldson, has announced he is to resign from his post next May after nearly 12 years in the role.
In his resignation letter to Sir Gus O'Donnell, the head of the civil service, Sir Liam reflected on some of the challenges he has faced over his tenure.
Most recently, Sir Liam has headed up the government's swine flu pandemic plans and has often been outspoken in defending them. He has told ministers that if the pandemic worsens in the coming months, he will consider staying on past May.
Sir Liam's influence on the health and wellbeing of Britain is visible in almost every facet of modern life, from possible reforms to alcohol pricing, to the introduction of smoke-free zones. He has often been at the forefront of controversial campaigns surrounding the impact of Britain's lifestyle choices.
In his resignation letter, Sir Liam wrote: "I have been immensely privileged to serve in this post over the past nearly 12 years.
"I have been pleased to see many of my policy recommendations - stem cell research, smoke-free public places, reforms to the General Medical Council, changes to consent for organ and tissue retention and the creation of the Health Protection Agency - carried forward into legislation."
"Sir Liam has made many valuable contributions to the good health of us all, and many thanks to him for taking a stand when it wasn't easy - but he did it! We trust the one who fills his post will be as diligent and committed as he was" - Mabel E. Farr, N Ireland