In 1909 he became a member of Paddington Borough Council, In 1910 he was elected to the London County Council as a Municipal Reform Party councillor representing North Hackney. He remained a member of the council until a few months before his death, becoming an alderman in 1931. He served as Chairman of the London County Council in 1925 - 1926, during which term he was knighted "for political and public services".
During the First World War he served in the Royal Garrison Artillery, reaching the rank of captain.
The Wikipedia page on his son EF WArburg is here .