Colchester in Essex, showing boundaries used from 1918 to 1950.
Following their review of parliamentary representation in Essex, the Boundary Commission for England created a modified Colchester constituency formed from the following electoral wards
Berechurch, Castle, Christ Church, Harbour, Highwoods, Lexden, Mile End, New Town, Prettygate, St Andrew's, St Anne's, St John's, and Shrub End. These boundaries came into effect for the 2010 general election.
From 1997 to 2010 the seat had very similar boundaries.
Once the basis for one or two semi-rural seats, the modern-day Colchester constituency is a compact, urban core, containing the town centre and surrounding neighbourhoods.
The seat has one of Britain's largest residential military populations, but the non-military vote in Colchester has swung further in favour of the Liberal Democrats since 1997 when Bob Russell was elected for the party with a small majority. Russell has increased both his total vote and percentage share in each of the succeeding elections. In the 2010 election it was the only non-Conservative seat in Essex. He was defeated in the 2015 general election by the Conservative candidate Will Quince, winning with a 11.5% majority. This made Clacton the only seat in Essex held by a non-Conservative MP - with Douglas Carswell winning the constituency for UKIP.
^Webster and Rebow were re-elected in 1714, but on petition the result was reversed and Gore declared to have been duly elected instead, following a dispute over whether foreigners could be made freemen of the borough and thereby acquire voting rights
^Webster was re-elected in 1710, but on petition the result was reversed and Gore and Corsellis declared to have been duly elected instead, following a further dispute over foreign freemen's voting rights
^At the election of 1741, Olmius and Martin were returned as elected, but on petition their election was declared void and their opponents, Savill and Gray, declared elected in their place
^At the election of 1754, Gray was re- elected, but on petition his election was declared void and his opponent, Rebow, declared elected in his place
^ abOn petition, Potter's election was declared void on the grounds of defective qualification and his opponent, Affleck, declared duly elected