David Brewer's career was with the insurance brokers, Sedgwick, subsequently Marsh, beginning in 1959. In 1976 he went to Japan to open their office in Tokyo, and lived there for three years.
On his return, he became involved with China, when Deng Xiaoping started his Open Door Policy, and he made his first visit in 1981, when he established the first office of any insurance broker, in Beijing. During the last thirty five years he has visited China over 130 times. He has a long association with the China-Britain Business Council, of which he was Chairman from 2008 to 2014.
In the City of London, he was a Member of the Court of Common Council from 1992-1996, when he became an Alderman, for the Ward of Bassishaw, from 1996-2000. He was a Magistrate in the City of London for 27 years, from 1979. He was a Sheriff in 2002-2003, and was Lord Mayor of the City of London for the year 2005-2006.
In 2008 he was appointed by Her Majesty The Queen to be Her Majesty's Lord-Lieutenant of Greater London, a position which he held until 2015. During this period he was President of the Greater London Reserve Forces and Cadets Association.
In 2006 he was presented with the Magnolia Gold Award by the Mayor of Shanghai, and in the same year he was awarded the Japanese Order of the Rising Sun.
His mother Livery is the Merchant Taylors' Company, of which he was Master in 2001-2002. He is an Honorary Bencher of Gray's Inn. He is currently Chair of the St. Paul's Cathedral Council.
In June 2016, David was appointed a Knight of the Garter by Her Majesty The Queen.
Sir David is a CNED.