A beaming Nigel Farage turned up in Downing St today - Theresa May’s last as Conservative leader – to stage a political stunt after his Brexit Party narrowly lost to Labour in the Peterborough by-election.

Unexpectedly, the party leader arrived at No 10 and posed for the cameras outside the famous black door with his fellow BP MEP Richard Tice, holding a letter, urging the Prime Minister – who is in her Maidenhead constituency - to take up his offer of help in the Brexit process.

"While the Government work out who the next prime minister is, we've only got less than five months until we're meant to leave the EU. We would love to start helping now. We want responsibility, we want to get involved," declared Mr Farage.

The Herald:

READ MORE: Labour sees off challenge from Brexit Party to win Peterborough by-election

The letter, which was also addressed to the leadership candidates, said: "We should firstly review the state of the no deal preparations and help advance them as required to give confidence to the nation that we will be fully ready."

It called for a WTO Brexit and also made clear Britain should not have to "beg for another delay beyond October 31".

The suspicion among Westminster-watchers is that the BP leader had planned his Downing St visit on the expectation of having won the Peterborough seat. Mr Farage, when asked about Mrs May’s time as Tory leader, said he would not be discourteous on her final day in the job; but his very presence on her doorstep was meant to underline a political message.

Despite the by-election result, in which the Tories were pushed into third place, contenders to succeed the Prime Minister warned of the dangers to their party if Brexit were not delivered.

Jeremy Hunt, the Foreign Secretary, said the result showed there was "no future" for the Conservatives unless the UK's EU withdrawal was completed before a general election.

Boris Johnson, his predecessor at the Foreign Office, warned: "Conservatives must deliver Brexit by October 31 or we risk Brexit Party votes delivering Corbyn to No 10."

A similiar message was delivered by Dominic Raab, the former Brexit Secretary, who insisted that failure to deliver Brexit by October 31 "would not only break our promise to voters, it risks delivering Jeremy Corbyn by the backdoor".

Having declared that the by-election result had "fundamentally changed" British politics, Mr Farage claimed a sort of victory in the wake of the result, which saw Labour narrowly hold onto the Cambridgeshire seat by just 683 votes.

Peterborough, which voted 61 per cent for Leave in the 2016 referendum, had been regarded as potentially fertile ground for the new party; expectations were high that the Brexit Party would have its first MP by today.

But with a relatively high turnout for a by-election of 48.4 per cent, it was unable to match Labour's organisation on the ground. Sources suggested Jeremy Corbyn’s party had “thrown everything, including the kitchen sink” at it.

Stressing how the Brexit Party was just two months old, he claim it had lost because Tories had not voted tactically to keep Labour out. "The danger is that, in seats like this, the Conservatives split the Leave vote," the MEP declared.

The result came as a huge relief for Labour after its dismal showing in last month's European elections amid complaints that the party had failed to offer a clear line on Brexit.

Mr Corbyn, who turned up in Peterborough to savour his party’s victory, said it was a "great win" and represented a rejection of the Conservatives' "disastrous" handling of Brexit.

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"In this key seat, the Conservatives have been pushed to the margins," he declared.

"This result shows that, in spite of the divisions and deadlock over Brexit, when it comes to a vote on the issues that directly affect people's lives, Labour's case for real change has strong support across the country," insisted the party leader.

He added Labour was ready for a general election and warned his opponents that the party should be written off "at your peril".

Labour won 10,484 votes to the BP’s 9,801, with the Tories on 7,243 votes in a seat which has traditionally been a two-way Conservative-Labour marginal. The Liberal Democrats were fourth with 4,159, while the Greens came fifth with 1,035 votes.

However, Labour's vote share fell by more than 17 percentage points from the 2017 General Election while the Conservatives were down by more than 25 percentage points.

In her victory address, winning Labour candidate Lisa Forbes hailed the result as a defeat for the BP's "politics of division".

"Despite the differing opinions across our city, the fact that the Brexit Party have been rejected here in Peterborough shows that the politics of division will not win," she said.

Defeated Brexit Party candidate Mike Greene admitted he had been unable to match Labour's established organisation in the constituency.

However, he insisted the party would continue to build on the momentum from its triumph in the European elections when it topped the poll.

"Two parties have been ruling this country for decades. That is not happening any more. We were ahead of the Tories, only 683 votes behind Labour," he told Sky News.

"They have decades of data. We had nothing just four weeks ago. We did not have the vote numbers they had. We didn't have the voting history they have.

"We will be back. Let's see what does happen in the next General Election," he added.

The by-election was called after Peterborough's previous MP, Fiona Onasanya, was forced out after she was jailed for lying about a speeding offence.

She was elected as a Labour MP in 2017 with a wafer-thin majority of 607 but was suspended from the party after she was sentenced.

Among local Tory activists there was frustration that the continuing turmoil over Brexit meant they were unable to take advantage of Labour's difficulties.

Wayne Fitzgerald, Chairman of the Peterborough Conservative Association, said it was now essential that the party committed to taking Britain out of the EU, even if it meant no deal.

"Parliamentarians in Westminster are against the will of the people," he told Sky News.

"The Conservatives must de-select every MP who will not accept a WTO[World Trade Organisation] Brexit if it comes to that.

"If Boris or whoever is leader doesn't do that, Mr Farage will sweep to 450 seats in the next General Election," added Mr Fitzgerald.

In a separate development, Michael Gove, the Environment Secretary, received a boost to his campaign for the leadership, as Kemi Badenoch, Tory Party vice-chairman, announced she was quitting her post at Conservative headquarters to join his campaign.

Meanwhile, Downing St was playing down any dramatic developments today as Mrs May ends her formal role as Tory leader; although she will continue as acting leader until her successor is chosen. There is expected to be an exchange of letters with the executive of the party’s backbench 1922 Committee.

The call for nominations to succeed the PM opens at 5pm.

The timetable is -

*Monday June 10. Nominations will be received by the 1922 Committee between 10am and 5pm.

Candidates from the 313 Conservative MPs will require a proposer, a seconder and six other MPs to support their candidacy to continue to the first ballot.

*Tuesday June 11. The first round of hustings begins for candidates who reached the threshold with all Conservative MPs in attendance.

*Thursday June 13. The first ballot takes place. Any candidate receiving 16 votes or fewer will be eliminated. The results are announced at 1pm.

*Sunday June 16. Krishnan Guru-Murphy will host a leadership debate among the remaining candidates on Channel 4.

*Monday June 17. Second round of hustings in front of Conservative MPs with the remaining candidates.

*Tuesday June 18. The second ballot. Any candidate receiving 32 votes or fewer will be eliminated. The results are announced at 1pm.

At 8pm, Emily Maitlis will host a Conservative leadership debate entitled Our Next Prime Minister on BBC One.

*Wednesday June 19. The third ballot, where the candidate with the fewest votes is eliminated. The results are announced at 6pm.

*Thursday June 20. The fourth and fifth ballots which will continue until two candidates remain. The 1922 Committee says it has provision for further ballots but this is unlikely. The results are announced at 1pm and 6pm respectively.

*Saturday June 22. With two candidates, Conservative Campaign Headquarters will begin the membership hustings process for party members. The party will aim for the hustings to take place in all 12 regions of the UK.

*The week commencing July 22. A new leader will be announced following the ballot of about 160,000 Conservative members. He or she will begin to form their new Government with appointments to the Cabinet announced first and lower ranks in the subsequent days.