As the Labour Party’s biggest financial backers, Unite the Union is one of the most powerful trade unions in the UK today.
Its former boss Len McCluskey was a key ally of former Labour leader Jeremy Corbyn - although his successor Sharon Graham has threatened to cut ties with the party in the wake of its move towards the political centre under Sir Keir Starmer.
But Unite is facing a major crisis after it was raided by police as part of a criminal investigation.
So what exactly are the police investigating at the trade union - and what has it said about the raids?
Here’s what you need to know.
What is Unite the Union?
Unite is the second biggest trade union in the UK - behind Unison - with more than 1.2 million members across sectors, including construction, logistics, manufacturing and transport.
It is Labour’s single largest donor - providing millions of pounds in backing, including £3 million in the lead up to the 2019 general election.
Between 2011 and 2021, its general secretary - i.e. its leader - was Len McCluskey.
Mr McCluskey was a key backer of Jeremy Corbyn and helped to turn the Labour Party towards a more left wing agenda than it had had under previous leader Ed Miliband.
When Sir Keir Starmer became Labour leader in 2020, Mr McCluskey cut Unite’s funding by around 10%.
Upon his retirement, Sharon Graham became Unite’s new boss and has threatened to remove all of the trade union’s financial backing for Labour.
A pay row in Coventry between the Labour-led council and bin lorry drivers led Ms White to tell protesters the financial support for the UK’s main opposition party “is now under review."
Sir Keir Starmer told the BBC he was: "not going to be influenced by those who say we’ll only provide money if you do ‘x’."
Why did police raid Unite Union?
It emerged this week that police had raided Unite the Union’s London headquarters in Holborn on Wednesday (6 April).
Sky News reported 15 to 20 officers entered the premises and left the building with boxes of files, paper and a computer.
Two police vans and several unmarked police vehicles were involved in the operation.
Addresses in South Wales, Powys (mid-Wales), North Wales, Merseyside, Cheshire, and Northamptonshire were also searched.
Police have said their criminal investigation is looking into allegations of bribery, fraud and money laundering.
In a statement, South Wales Police - which appears to be leading the investigation - said: “South Wales Police has executed warrants as part of an investigation into allegations of bribery, fraud and money laundering.
“The warrants were executed on Wednesday 6th April at addresses in the South Wales, Metropolitan, Merseyside, Cheshire, North Wales, Dyfed Powys and Northamptonshire police force areas.
“The joint investigation with Her Majesty’s Revenue and Customs is continuing and a number of suspects will be interviewed in due course.”
A spokesperson for the force did not reveal who will be questioned and said no-one had been arrested at this stage.
What has Unite Union said about the police raid?
The union said one of its employees is the subject of the criminal investigation.
It confirmed that it was this anonymous person’s office at its London HQ that police had searched on Wednesday.
A Unite spokesperson said: “A Unite employee is subject to a criminal investigation by the police. On Wednesday 6th April, the employee’s office at Unite HQ, in Holborn, London, was accessed and searched by the police under warrant.”
It has revealed no further details about what has happened.