From the Wikipedia page 
Bexley was a parliamentary constituency centred on the Bexley district of south-east London. It returned one Member of Parliament to the House of Commons of the Parliament of the United Kingdom.
The constituency was created for the 1945 general election, from parts of the Chislehurst and Dartford seats, and abolished for the 1974 general election and replaced by two new constituencies of Bexleyheath and Sidcup.
The MP when the constituency was abolished, the then Conservative Prime Minister Edward Heath, fought and won the new Sidcup constituency in 1974. He went on to represent the new seat of Old Bexley and Sidcup from 1983 until he retired from parliament in 2001 after being an MP for 50 years.