Boris Johnson and his close allies, Nadine Dorries and Nigel Adams, all announced their resignations within 24 hours of each other at the end of last week.

But standing down as an MP isn’t quite as simple as handing in a resignation letter. Parliament runs on rules dating back hundreds of years, and there is a rather arcane process for standing down.

Here’s everything you need to know about this summer’s by-elections after confirmation of the polling day dates for Mr Johnson and Mr Adams’ seats.

What triggers a by-election?

A by-election is caused when a parliamentary seat is left empty. This can happen for various reasons including an MP resigning, dying or being declared bankrupt.

In certain circumstances, such as if an MP is suspended from parliament for more than 10 days, a by-election can also be triggered by a “recall petition”. If 10% of registered voters in the constituency sign the petition, an election is held.

However, MPs aren’t formally allowed to resign.

Boris Johnson verdict is a hammer blow to Rishi Sunak’s hopes of maintaining a fragile peace in the Tory civil war

Boris Johnson has been damned but he may have more grenades to throw

Partygate report: The key findings of privileges committee that sealed Boris Johnson’s fate

Jacob Rees-Mogg rules out Johnson comeback before next election – politics latest

Why can’t an MP just quit?

An MP can’t simply resign because of a tradition that dates back to the 17th century. Instead, they must be disqualified from holding their seat.

To be disqualified, the MP must apply for a role in the paid office of the Crown. This means they automatically lose their seat because working for the Crown is not seen as impartial.

Essentially, the process ensures that the government is kept separate from the monarchy.

There used to be several roles used for this reason, but only the titles of the Crown Steward and Bailiff of the Chiltern Hundreds and the Crown Steward and Bailiff of the Manor of Northstead remain.

These roles don’t come with any responsibility or pay.

Mr Johnson is one of few people in history who has now held both titles, having used this process to resign when he was elected mayor of London in 2008.

Ms Dorries has not yet applied for one of the offices of the Crown, meaning she is still a sitting Tory MP, despite announcing her resignation “with immediate effect”.

Moving the writ

The official process of an MP being disqualified from their seat is triggered by “moving the writ”. This is when the chief whip of the political party the resigning MP belongs to puts forward a motion to the Speaker.

They ask “that the Speaker do issue his Warrant to the Clerk of the Crown to make out a new Writ for the electing of a Member to serve in this present Parliament for the constituency of… in the room of…”

The Speaker puts this to MPs and if they agree, the writ then passes through the Commons and ends up with the Returning Officer in the local constituency who oversees the by-election.

The writ is typically issued within three months of the MP resigning from their seat and in doing so, the date of the by-election is fixed.

Related posts:

‘A true hero’: Lorry driver praised for parking under motorway bridge to stop man jumping off it Neo-Nazi student who carved swastika into girlfriend’s buttocks guilty of terror offences UK records 133 more COVID deaths and another 34,950 cases Stars ready to join Prince William for ceremony recognising best ideas for tackling climate change ‘Have you never wanted to moonie a speed camera?’ Police fail to see funny side as they arrest terminally ill man Met Police investigating death threats against Starmer following PM’s Savile ‘slur’ PM goes nuclear in bid to build case for energy independence plan Rebekah Vardy v Coleen Rooney: The ‘Wagatha Christie’ case explained Scammers pretend to be striking paramedics to trick people into giving donations Police release man arrested over New IRA claim on detective’s shooting Braverman ‘encouraged’ by talks with human rights court in push to have migrants sent to Rwanda ‘Butchered’ by ‘trophy hunters’: Hunt for missing head of rare shark which washed up on UK beach