While Keir Starmer measures the curtains for his new life at No.10, there are signs that his ambitious Left-wing deputy might already be laying the groundwork to replace him as Labour leader.

In public at least, Starmer and Angela Rayner are united. And with the polls pointing to a landslide Labour victory, they are preparing to hit the ground running.

But behind the scenes, their relationship has been fractious to say the least.

As Rayner readies herself to be Britain’s first female deputy prime minister, she is acutely aware that most powerful woman in Starmer’s putative new cabinet will not be her at all, but Rachel Reeves the incoming chancellor.

‘It stings that Ange is not “inner circle”,’ says my Labour mole.

But Rayner has a trump card. Not only is she the elected deputy leader of the Labour Party – a role from which Starmer is unable to oust her – she is the darling of Labour’s grassroots membership.

And it’s her popularity with party members that might explain four mysterious internet domain names pointing to a future Rayner leadership challenge.

The sites are: ‘raynerforpm.co.uk’, ‘angelaforpm.co.uk’, ‘angela4pm.co.uk’ and ‘rayner4pm.co.uk’ – all registered by a person or persons unknown.

Intriguingly, they were set up on July 11, 2022, which was just three days after Rayner and Starmer had been cleared of breaching lockdown rules over a beer and takeaway curry controversially consumed with staff during a Hartlepool by-election campaign in April 2021.

Or were the domain names established by an admirer of Rayner? Does Rayner know of their existence?

For its part, Labour has denied the domain names have anything to do with its deputy, while a source added: ‘There is only one party leader whose position is in any doubt and that is the Prime Minister, with Tory leadership candidates already jostling for position.’

Perhaps they were set up by an enterprising politico who will be able to sell them to Team Rayner if and when there is a leadership contest?

Regardless, Angela Rayner seems surprisingly well prepared for such an eventuality, not least because it is Labour Party members who elect the leaders.

Since the start of the year, Rayner has banked donations of £47,650 to run her political office.

A former shop steward for Unison, one of the biggest trade unions in the country, Rayner is also supported by staff seconded by the union movement. In fact she has a team of eight on her payroll including a ‘chief-of-staff’, a private secretary and a number of policy advisers.

In September 2022, Rayner received a £22,000 donation to fund a ‘branded vehicle and related services’.

‘She already has the air of a deputy prime minister,’ said one Labour source.

There was scarcely concealed glee in her camp yesterday when a poll showed that Rayner, one of the few frontbenchers to describe herself as a ‘socialist’, has emerged as the most popular choice among Labour voters to succeed Starmer.

If she does, however, the rest of the country should be worried.

Take, for example, Rayner’s comments in an online meeting with Left-wing activists in 2020.

Not only did she praise former leader Jeremy Corbyn as ‘being on the right track’, she went further and endorsed the hard-line policies of Corbyn’s shadow chancellor John McDonnell, who has never hidden his Marxist leanings and once gleefully admitted he had campaigned for the ‘overthrow of capitalism’.

The party must persist with the work McDonnell had been doing, she told the WebRoots Democracy Festival.

Rayner had been ‘as worried and apprehensive as anybody [about Starmer],’ she explained. ‘I didn’t want to go back to magnolia politics, I thought that is going to be really bad, and...this is going to be terrible.’

But, ‘reassuringly’, she had found that Starmer agreed with her on key points.

‘I push him to push a bit more at times,’ she said, because Labour had to change Britain in ‘a fundamental way… not just, like, tweak it round the edges.’

She went on: ‘If we don’t continue with the work that John McDonnell was doing... then I think the Labour Party’s finished.’

In 2015 there was uproar in the Commons when, as shadow chancellor, McDonnell jokingly flicked a copy of Chinese dictator Chairman Mao’s ‘Little Red Book’ across the Despatch Box to George Osborne as he criticised the government’s relationship with China. Printed in its millions, the book was the notorious propaganda aid containing the key tenets of Mao’s Communist regime – which is conservatively estimated to have caused 60 million people to starve to death.

McDonnell even recited passages in the Commons.

The toe-curling exchanges were edited out of the official Labour Party film of the proceedings just a few weeks later.

Praise for the work of McDonnell, then, will dismay Starmer’s team, which has fought to distance him from the Corbyn era.

Starmer served in Corbyn’s shadow cabinet and was architect of his second Brexit referendum plan. He has attempted to justify staying in the Corbyn shadow cabinet – even though many of his colleagues, such as Yvette Cooper, quit or refused to serve in the first place in protest at his hard-line views – by claiming that he never thought Corbyn would win the 2019 election.

In 2021 there was another revealing insight into Rayner’s views when the police tried to assist officials who were trying to deport two illegal migrants in Glasgow.

When a crowd intervened, and the officials released the two migrants, Rayner tweeted: ‘Solidarity with the people of Glasgow.’

In the same year, Starmer attempted to demote Rayner during a botched shadow cabinet reshuffle.

But Rayner emerged from the row with an improved job title and expanded policy brief.

She is now deputy leader, shadow first secretary of state, shadow chancellor of the Duchy of Lancaster, and shadow secretary for the future of work.

Labour’s 131-page manifesto states that it will be working closely with trade unions and employers to promote better rights for workers under a proposed ‘New Deal’ for employment.

The changes will see the dismantling of any Tory legislation on employment since 2010.

One proposed change could ban bosses from contacting staff outside office hours. Another could be to enshrine in law the right to work from home.

The measures have been dubbed a ‘skivers’ charter’ by the Tories.

With one eye on the party membership, Rayner admits the ‘New Deal’ was written hand-in-hand with her trade union paymasters.

‘This is vital... it was developed in collaboration with you – the trade union movement – and it will be delivered with you,’ she has said.

‘Work will finally pay, rights will be properly enforced, and crucially it will strengthen the role of trade unions in our society.’

Labour have selected at least 329 new candidates who are trade union members, with a significant number working as senior trade union employees.

They include Laurence Turner the candidate in Birmingham Northfield who is head of policy at the GMB union which co-ordinated the strike by ambulance staff last year – the biggest walkout in the history of the NHS.

Antonia Bance, the candidate in Tipton and Wednesbury, is head of campaigns at the TUC, which has backed all the strikes in the NHS.

Lee Barron, who is standing in the Northamptonshire constituency of Corby, is the Midlands Regional Secretary of the TUC.

He previously named his Twitter profile ‘unionbarron’.

Rayner’s plans will be music to the ears of this next generation of Labour MPs. The election could result in the highest number of trade union officials and members elected to Parliament in history.

So who will the trade unionist MPs represent? Their constituents? Or the radical Left-wing trade unions – and their trade unionist in chief, Angela Rayner.