What exactly happens when an MP defects to another party?

Ms Elphicke is far from the first MP to change sides between elections, but it was incredibly rare - until recently - for a member of the governing party to switch to the opposition.

She is the third Tory to do so in just over two years, following Christian Wakeford in 2022 over the partygate scandal and Dan Poulter just two weeks ago over the Tories' handling of the NHS.

Before that, it hadn't happened since 1995, when Alan Howarth became the first ever Conservative to cross to Labour on the eve of his party conference, citing the "divisiveness" of policies under John Major's leadership.

Only three MPs in the past 25 years have gone the other way - from main opposition to government - all leaving the Conservatives to join Labour.

Defecting to smaller parties happens more often, such as moves from both Conservative and Labour to Change UK during the Brexit years, or Douglas Carswell and Mark Reckless heading over to UKIP ahead of the referendum.

And the SNP's Lisa Cameron moved onto the Tory benches in 2023 over claims of mistreatment and bullying by her now former party colleagues.

But it is still not common practice, with only 202 cases of MPs changing allegiance since 1979, according to the Institute for Government - and over half of those being because they were suspended or kicked out of their existing party, rather than resigning to join a different side.

The moment of defection itself often comes as a surprise, with negotiations happening behind closed doors, and the key piece of theatre occurs when a member "crosses the floor" - meaning they switch the part of the Commons' benches they sit on to join their new party.

And despite the usual loud cries from their former party that they should call a by-election to give voters a choice over which rosette their MP wears, there is no rule forcing them to.

The House of Commons Library puts the convention down to the arguments of a rebellious MP from the late 18th century, Edmund Burke, saying members are a representative of their constituency, rather than a delegate of any party.

"Historically, the Commons has acted on the principle that all members of the House of Commons are individually elected, and voters put a 'cross against the name of a candidate'," it says.

"While decisions on candidates may be affected by their party labels, MPs are free to develop their own arguments once elected, until it is time to face the voters in the next general election."

However, some choose to go to the public anyway, including both Mr Reckless and Mr Carswell who both won their by-elections - although the former lost his seat at the 2015 general election and the latter quit UKIP in 2017, pledging to vote Conservative in the election that year.

There is no sanction for the move either - though MPs who have defected often speak of the cold shoulder they receive from their former colleagues in the corridors, or even from their new party, who can be untrusting of their conversion to their cause.

It is often the case that MPs who have changed party lose their seat at the next election when voters have their say, or choose to stand down when the poll comes - as is the case with Ms Elphicke and Mr Poulter.

If they do wish to stand again under their new banner, however, they have to go through the standard selection process carried out by local constituency parties, usually involving a vote for their preference, and be approved by the leadership before being named the electoral candidate - as has been the case for Mr Wakeford.