ONE of Theresa May's closest allies, Damian Green, has paid tribute to her as her departure draws closer.

The Prime Minister has arrived in Downing Street where she is understood to be meeting 1922 Committee chairman Sir Graham Brady after a cabinet revolt over her latest Brexit plan and the delay of the Withdrawal Agreement Bill (WAB).

Tory backbenchers' representative Sir Graham is expected to insist that she should set out when she will resign, with a 1922 Committee source telling the Press Association Mrs May's departure date is likely to be June 10.

Meanwhile, one of her closest allies paid tribute to her leadership and spoke openly about who should succeed her on BBC Radio 4's Today programme.

Her former de facto deputy Damian Green said a difficult hand to play was made impossible by losing her majority in the snap general election.

He said: "Suddenly and unexpectedly becoming Prime Minister after the seismic shock of the Brexit referendum meant she was dealt an extremely difficult hand to play.

"The truth is, having an election a year later, which cut the Conservative Party's majority, then at that point it is impossible."

Green added she could not recover from the resignation of former Brexit secretary David Davis in July last year.

He said: "I think the key point where it went off the rails was when David Davis resigned from Cabinet.

"I think being able to have a deal that kept him and probably Boris Johnson inside would have made all the difference - that seems to have been the turning point."

Meanwhile, former Middle East Minister Alistair Burt said he could vote for Boris Johnson to take over from May at Number 10.

When asked whether he could back Johnson, he told the Today programme: "The answer to the question for almost all the candidates is yes.

"I would find it very difficult to support a candidate who said it was in Britain's best interest to leave with no deal, leave straight away, WTO...

"I don't expect any candidate really to say that."

Meanwhile, Helen Grant, Conservative vice chair for Communities, resigned to "actively and openly" support one of the new leadership candidates.

In a letter to the Tory Party chairman Brandon Lewis, she said: "Regrettably, I must now give notice of my resignation because I wish to actively and openly support one of the new leadership candidates and would not want there to be any perception of a conflict between the candidate's campaign and my role at CCHQ.

"The PM has, of course, said she will be leaving, a decision that I respect and believe to be right. I have a close relationship with my local Association and they are fully supportive of this decision."

The Prime Minister's private meeting with Sir Graham could be the moment she sets the date for her exit from Downing Street.

A 1922 Committee source said they expected June 10 to be the day May chooses.

"Hopefully what will happen is she will stand down as Tory leader I think on or before June 10, and she will hopefully remain as caretaker Prime Minister until such time as a new Tory leader is elected," they said.

"My feeling is that she will stay until June 10."

The source said a new leader would ideally be in place by the end of the summer to get a Brexit deal through Parliament before October 31, the date currently set for the UK's exit from the European Union.

May's leadership appears fatally damaged by the reaction to her latest Brexit deal, which offers MPs a vote on whether to hold a second referendum and a choice which could leave the UK in a temporary customs union with the EU – both measures which are unacceptable to Tory Eurosceptics.

The scale of Cabinet anger at the legislation – which led to Andrea Leadsom's resignation as leader of the House of Commons on Wednesday night – was made clear by two of Mrs May's most senior ministers.

Foreign Secretary Jeremy Hunt is understood to have told the Prime Minister to ditch the WAB completely, saying it was clear it would not pass.

It was a "step too far" to ask Tory MPs to vote for it under those circumstances, he told the Prime Minister.

Javid had a "frank discussion" with the Prime Minister about the plan, making it clear he does not believe the Government should be "paving the way" for a second referendum.

The WAB had been due to be published on Friday but that has been delayed in a sign of the chaos at the top of the Government.

MPs were told that the Government now intends to publish the Bill in the week beginning June 3.

In a sign that May's departure may come within weeks, rather than days, the Foreign Secretary said he expected her to still be Prime Minister when US president Donald Trump visits the UK on June 3.

In response to a question following a speech at the National Cyber Security Centre, he said: "Theresa May will be Prime Minister to welcome him and rightly so."

Digital minister Margot James said May was "being hounded out of office because Parliament will not make a decision and the parties just have an inability to compromise" over Brexit.