Fifteen candidates are facing voters at the ballot box in the Peterborough by-election on Thursday in a contest that will have wide political ramifications.
The election of a new MP came about after local people effectively sacked their former Member of Parliament, Fiona Onasanya in a recall petition.
Ms Onasanya had been jailed for perverting the course of justice by lying to police over a speeding offence.
She won the Peterborough seat for Labour at the 2017 General Election by beating the sitting Conservative MP Stewart Jackson by 607 votes.
That made it the most marginal Labour constituency in the Anglia region.
Normally Peterborough constituency would be straightforward battle between Conservative in Labour with each party winning the seat alternately since the 1950s.
The situation is more complicated in a by-election with voters tending to register a protest.
An added factor is the recent political turmoil punishing both the main parties at Westminster and seeing a rise in support for the newly formed Brexit Party along with the Liberal Democrats and Greens.
Sir Harmar Nicholls was the Conservative MP for Peterborough from 1950 until 1974 when Michael Ward took over for Labour.
Conservative Sir Brian Mawhinney held the seat from 1979 until 1997. Helen Clark was the Labour MP from 1997 until 2005 and Tory Stewart Jackson held the seat from 2005 until 2017.
Peterborough is renowned for close contests. In the 1966 General Election, the Conservative beat Labour by just three votes after seven re-counts.
Candidates in the Peterborough by-election
Paul Bristow (Conservative)
Lisa Forbes (Labour)
Stephen Goldspink (English Democrats)
Mike Greene (Brexit Party)
Howling Laud Hope (Official Monster Raving Loony Party)
Pierre Kirk (UK European Union Party)
Patrick O'Flynn (SDP Fighting for Brexit)
Dick Rodgers (Common Good: Remain in the EU)
Tom Rogers (Christian Peoples Alliance)
Beki Sellick (Liberal Democrats)
Bobby Elmo Smith
Peter Ward (Renew)
Joseph Wells (Green Party)
John Whitby (UKIP)
Peterborough lies halfway between the East Anglian coast and the Midlands.
Its good road and rail links have turned it into a major distribution centre.
The East Coast Mainline provides travel to London in 50 minutes and, as a result, Peterborough has developed into something of a commuter town.
In the recent local elections at the start of May, the Conservative lost their slender overall majority on Peterborough City Council but continue to run a minority administration.
The parliamentary constituency of Peterborough covers only part of the area of the Peterborough City Council local authority.
Click to watch a report on the Peterborough by-election by ITV News Anglia's Political Correspondent Emma Hutchinson
It is estimated that more than 60% of voters in the Peterborough constituency voted to leave the European Union in the 2016 Referendum.
In the most recent European Elections on 23 May 2019, the Brexit Party took the biggest slice of the votes in the Peterborough district with 38% of the votes.
But that was a proportional representation election with all the votes in Peterborough being added to a wider East of England total.
In the local elections at the start of May when the Brexit Party were not standing, the Conservatives took 32% of the votes with Labour second on 28%.
The Conservative made a net loss of three council seats with the Liberal Democrats gaining two seat, Labour gaining one seat and the Greens doubling their number to two.
UKIP lost their last remaining council seat.
Polling stations are open in Peterborough from 7am until 10pm on Thursday 6 June 2019.
The result is expected to be announced in the early hours of Friday morning.