Sir Mike was a hospital physician for more than 20 years. Notably, he was a consultant medical oncologist between 1986 and 1995 and Prof of Palliative Medicine at Guy's and St Thomas' Hospitals between 1995 and 1999.

In 1999 Sir Mike was appointed as the first national cancer director at the Department of Health. He led the development and implementation of the NHS Cancer Plan in 2000, the Cancer Reform Strategy in 2007 and Improving Outcomes: A strategy for cancer in 2011.

He became the CQC's first chief inspector of hospitals in July 2013 and led the development and implementation of a new approach to hospital inspection. Sir Mike retired from this role at the end of July 2017.

He led two major reviews for NHS England: A review of adult screening services (published 2019) and a review of diagnostic services (published October 2020). He is also a trustee of Cancer Research UK. In April 2022 he was appointed as chair of the UK National Screening Committee.

Subject to approval by the Health and Social Care Select Committee, Sir Mike will take over from the current chair Ian Dilks once his appointment ends.