He was first elected to city council in 1955 as the
alderman for Ward 8, in east-end Toronto, that included
The Beaches neighbourhood. He served until 1958, then he was elected to the
Toronto Board of Control – the city hall executive council – in 1959 and served until 1961. He was elected mayor of Toronto in December 1962 and took office on New Year's Day 1963. On 19 November 1963, Summerville suffered a fatal heart attack while playing in a charity hockey game at the George Bell Arena in the west-end Toronto neighbourhood known as
The Junction. The fire department arrived about three minutes after it was called, but because ambulances in the area were already on call, an ambulance had to be dispatched from
Yonge Street at
Davenport Road and did not arrive until about 15 minutes after it was called, arriving at 8:55 p.m. At very high speeds, he was rushed to
St. Joseph Hospital in the High Park area, and died there at 9:05 p.m. Mayor
Philip Givens, who succeeded Summerville, called for an inquest into why the emergency response was so slow. The inquiry into the emergency response to his death found that the closest ambulance was not sent because its service did not have jurisdiction over The Junction and so was not called. That led to the creation of the Department of Emergency Services and the amalgamation of
Metropolitan Toronto's various local ambulance services. ==Funeral==