London deputy mayor Sir Simon Milton has died after a short illness at the age of 49.

Sir Simon, who was mayor Boris Johnson’s chief of staff, died in hospital yesterday. He was one of two openly gay deputy mayors in Mr Johnson’s administration.

Mr Johnson said: “He was a wonderful colleague and friend, and will be much missed by everyone who was involved in public life in this city.

“He was kind, he was decent, and he was universally acknowledged to be brilliant at his job. He was a widely admired leader of Westminster council, who played a key role in launching the first academy schools.

“He brought the same calm, logic and warmth to his role at City Hall. It is a great shock that Simon has been taken from us when he had so much still to offer.”

Sir Simon, who was knighted in 2006, entered politics while a student at Cambridge, where he became chairman of the university’s Conservative Association.

He served as the leader of Westminster city council for eight years before being appointed deputy mayor in 2008.

In 2007 he was elected chairman of the Local Government Association.

He is survived by his civil partner Robert Davies, a Westminster councillor. The couple were together for more than 20 years.