The Met police will not be saying who is fined or which events the fixed penalty notices relate to.

However, Downing Street has said before that it would confirm if the prime minister was facing a fine.

Fixed penalty notices are a sanction for breaking the law, and mean a fine, which needs to be paid within 28 days, or contested.

If someone chooses to contest the fine, the police will then review the case and decide whether to withdraw the fine or take the matter to court.

The police said they were attempting to progress the investigation, with a "significant amount" of material still to be assessed and that more fines could come in the future.

The police have been investigating 12 events that may have breached coronavirus lockdown rules, including at least three attended by Boris Johnson.

As part of their inquiries, they have sent out over 100 questionnaires to ask about people's participation in the events.

Reports of gatherings in Downing Street and Whitehall during the lockdown prompted public anger and several Conservative MPs called for the prime minister to resign.

However, since the outbreak of the war in Ukraine, some have withdrawn their demand.

Others have said they are withholding judgement until the police conclude their investigation, and an internal inquiry is published.

Mr Johnson had previously insisted that "guidelines were followed at all times".

He later apologised for attending a drinks party in the Downing Street garden in May 2020, but insisted that he believed it was a work event.

A No 10 spokesman said he did not believe Mr Johnson had misled the House of Commons, adding: "You will hear from the prime minister at the conclusion of the Met's investigation."

He added: "The PM's apology for how this was handled is a matter of record."

The spokesman also said Mr Johnson had not received a fine.

If either the prime minister or Simon Case - the country's most senior civil servant - got a fine, it would be made public, No 10 said.

Some of the political pressure has died down in recent weeks. Opposition parties are still calling on the prime minister to resign, but some Tory MPs are more reluctant because of the crisis in Ukraine.

There are though Conservatives who are deeply uncomfortable with the idea of lockdown parties while everyone else was being told not to mix. They will be watching to see who is fined - and how Downing Street reacts.

But whatever happens next, the police have now said they believe Covid laws were broken in government buildings where they were being set.

Remember in December, the prime minister insisted all guidelines had been followed - and denied parties had taken place.

A lot has changed in a few months.

Labour's deputy leader Angela Rayner said: "After over two months of police time, 12 parties investigated and over a hundred people questioned under caution, Boris Johnson's Downing Street has been found guilty of breaking the law.

"The culture is set from the very top. The buck stops with the prime minister, who spent months lying to the British public, which is why he's got to go."

Sir Ed Davey, leader of the Liberal Democrats, said "If Boris Johnson thinks he can get away with partygate by paying expensive lawyers and throwing junior staff to the wolves, he is wrong.

"We all know who is responsible. The prime minister must resign, or Conservative MPs must sack him."

A campaign group for bereaved relatives of people who died with Covid said the prime minister "should have resigned months ago over this".

In a statement, the group said: "It's crystal clear now that whilst the British public rose to the challenge of making enormous sacrifices to protect their loved ones and their communities, those at 10 Downing Street failed."

However, former health secretary Matt Hancock defended Mr Johnson had got "the big calls" right and was was "the best person to lead the country".

He added that he would stand by the prime minister even if he was fined by the police.

What are fixed penalty notices?

Fixed penalty notices (FPNs) for breaching Covid regulations do not lead to a criminal record - they're a low-level sanction - the equivalent of a minor speeding offence - to divert people from the courts.

Each of the Metropolitan Police's 20 decisions to issue FPNs in relation to "partygate" now goes to Acro, the criminal records office for England and Wales.

It will receive and process the payments required from each person who has been found to have breached the regulations.

That means there is an official record on the system - but it is not a criminal record that must be disclosed.

If someone doesn't pay an FPN, then it becomes more serious. The notice will be referred to the courts. In the worst case scenario, a magistrate could issue a warrant for someone to be arrested and hauled before them for non-payment.

Challenging an FPN is complicated and has been much criticised as opaque and potentially unfair by expert lawyers.

Sometimes an individual police force may reverse a decision after direct lobbying.

The alternative is to argue it out in court. But that is expensive - and losing leads to a criminal conviction as it's a criminal court ruling. And that's why most people faced with an FPN suck it up - and cough up.

When stories emerged about events held in government buildings during the Covid lockdowns, senior civil servant Sue Gray was asked to lead an inquiry.

She had been due to produce her full report into the parties last month, but had to delay publication when the police announced their own investigation.

Instead Ms Gray released her initial findings in which she criticised "failures of leadership and judgement" in government.

The police have been looking into 12 of the 16 events listed in her report. Mr Johnson is known to have attended at least three of the gatherings:

* 20 May 2020 in the Downing Street garden

* 19 June 2020 in the Cabinet Room for the prime minister's birthday

* 13 November 2020 on the departure of a special adviser

Sue Gray’s record of the gatherings

The government has faced intense pressure over gatherings held in and around Downing Street during Covid lockdowns. Senior civil servant Sue Gray has said that many of them “should not have been allowed to take place or to develop in the way that they did.” Here is what we know about them and the restrictions in place at the time:

15 May 2020

A photo from May 2020 showed the prime minister and his staff with bottles of wine and a cheeseboard in the Downing Street garden. When asked about it, Boris Johnson said “those people were at work talking about work”.

The rules:

Legal restrictions at the time said you could not leave your house without a reasonable excuse and government guidance was that you could meet one person outside of your household in an outdoor setting while exercising.

This event is not being investigated by the police.

20 May 2020

About 100 people were invited by email to “socially distanced drinks in the No 10 garden this evening”. Witnesses told the BBC the PM and his wife were among about 30 people who attended. Boris Johnson has declined to say whether he was among those there.

This event is being investigated by the police.

18 June 2020

A gathering took place in the Cabinet Office to mark the departure of a No 10 private secretary.

This event is being investigated by the police.

19 June 2020

On Boris Johnson’s birthday, up to 30 people gathered in the Cabinet Room at No 10 to present the prime minister with a birthday cake and sing Happy Birthday, according to a report by ITV News.

No 10 said staff had “gathered briefly" to "wish the prime minister a happy birthday", adding that he had been there "for less than 10 minutes”.

The rules:

Restrictions at the time banned most indoor gatherings involving more than two people.

This event is being investigated by the police.

13 November 2020

Sources told the BBC that Downing Street staff members attended a gathering with Carrie Johnson in the flat where she and the prime minister live. A spokesman for Mrs Johnson denies the party took place. There was a separate gathering in No 10 Downing Street on the same day to mark the departure of a special adviser.

The rules:

Eight days earlier Boris Johnson had announced a new lockdown in England. Indoor gatherings with other households were banned, unless they were for work purposes.

These events are being investigated by the police.

27 November 2020

A leaving event was held for No 10 aide, Cleo Watson, where people were drinking, and Mr Johnson made a speech, according to sources.

This event is not being investigated by the police.

10 December 2020

The Department for Education has confirmed it had an office gathering to thank staff for their work during the pandemic. It says drinks and snacks were brought by those who attended and no outside guests or support staff were invited.

The rules:

Eight days earlier, London had been placed in restrictions which banned two or more people from different households from meeting indoors, unless “reasonably necessary” for work purposes.

This event is not being investigated by the police.

14 December 2020

The Conservative Party has admitted that an “unauthorised gathering” took place at its HQ in Westminster. It was held by the team of the party's London-mayoral candidate, Shaun Bailey, who has since stepped down as chair of the London Assembly police and crime committee. The Metropolitan Police is to speak to two people who attended the party.

The gathering at the Conservative Party headquarters was described as ‘raucous’

This event was not included in Sue Gray's report.

15 December 2020

Multiple sources have told the BBC there was a Christmas quiz for No 10 staff last year. A photo - published by the Sunday Mirror - shows Boris Johnson taking part and sitting between two colleagues in No 10. Mr Johnson has denied any wrongdoing.

Mr Johnson was pictured in the No 10 library under a portrait of Margaret Thatcher

This event is not being investigated by the police.

16 December 2020

The Department for Transport has apologised after confirming reports of a party in its offices, calling it “inappropriate" and an "error of judgment” by staff.

The rules:

London moved into the highest tier of restrictions and Matt Hancock, who was health secretary at the time, said it was important “everyone is cautious” ahead of the festive period.

This event was not included in Sue Gray's report.

17 December 2020

A leaving party was held at the Cabinet Office for the outgoing head of the civil service Covid taskforce - the team responsible for drawing up coronavirus restrictions.

Kate Josephs, now chief executive of Sheffield City Council, apologised for the event, saying she was “truly sorry that I did this and for the anger that people will feel as a result”.

A second gathering was held in the Cabinet Office to hold an online Christmas quiz for the Cabinet Secretary’s private office.

A third gathering was held in No 10 Downing Street to mark the departure of a No 10 official

These events are being investigated by the police.

18 December 2020

Downing Street originally denied a report by the Daily Mirror that a party took place in Downing Street. However, a video obtained by ITV News showed the prime minister's then-press secretary Allegra Stratton, joking about reports of an event, saying: “This fictional party was a business meeting and it was not socially distanced.”

This event is being investigated by the police.

14 January 2021

A gathering was held in No 10 Downing Street to mark the departure of two private secretaries.

This event is being investigated by the police.

16 April 2021

Two parties were held by Downing Street staff at No 10, the night before Prince Philip's funeral.

One of the events was a leaving party for the PM's then director of communications James Slack, who has apologised for the event and acknowledged it “should not have happened at the time that it did”.

Boris Johnson was not at either party.

The rules

The rules had been eased in England on 12 April, but working from home continued to be recommended and socialising indoors with people from other households was not allowed. Meeting others outdoors was limited to groups of six people or two households.

These events are being investigated by the police.