When Sir Keir Starmer was asked if he was a socialist, there was a momentary pause before he replied “yes”. When the same question was put to shadow chancellor Rachel Reeves, she chose instead to describe herself as a social democrat.

With Labour deputy leader Angela Rayner there were no such hesitations or equivocations as she readily affirmed her socialist credentials – and for good measure suggested that Ms Reeves is really a believer too.

As the party’s new Red Queen, many will now be looking to her – like John Prescott before her – to stand as guardian of its traditional values in the face of a modernising leadership.

Certainly, the parallels with the Blair-Prescott era are striking. Like her predecessor, she worked her way up the hard way, leaving school at 16 and cutting her teeth as a trade union official before embarking on a career in parliament.

While she has not actually hit any voters, as the pugnacious Mr Prescott famously did, she has not been afraid to engage in old-fashioned class warfare, once describing the Conservatives as “a bunch of scum”.

As with Tony Blair and Mr Prescott, there have been tensions with her lawyerly leader – Sir Keir once tried to demote her, only to end up vastly extending the range of her shadow cabinet responsibilities.

She is now set to take charge of one of the most contentious elements of the new Government’s policy agenda, overseeing a major extension or workers’ rights with the creation of a new watchdog with powers to fine and prosecute errant employers.

It is a prospect that has some business leaders looking nervously over their shoulders, but that is unlikely to deter a politician who has never shied away from confrontation.

While Labour made much of Sir Keir’s hardscrabble upbringing during the course of the election campaign, it hardly compares with that of his deputy.

Ms Rayner grew up in the squalor of a rundown council estate in Stockport, her mother had bipolar disorder and was prone to self-harm, while her father was nearly always out of work.

I'm a pretty young woman, lots of red hair, and everyone expects me to be stupid when I walk into a meeting for the first time

She would go once a week with her two younger siblings to bathe at her grandmother’s flat because the family could not afford to pay for hot water. When she left school, having become pregnant, she was told she would never amount to anything.

After studying part-time for a vocational qualification, she took a job as a care worker for the local council, where she was put forward as a union representative.

“I was mouthy and I would take no messing from management,” she later recalled.

It was a move that set her on the path to a political career, rising through the ranks to became a full-time union convener, before standing successfully for the safe Labour seat of Ashton-under-Lyne in the 2015 general election.

At Westminster she identified with the “soft left” and in 2016 was given her first frontbench roll as shadow pensions minister by Jeremy Corbyn.

She was among the minority of Labour MPs to stand by him in the chaotic aftermath of the Brexit referendum when he faced a concerted push to oust him.

When he survived the ensuing leadership challenge, her reward was promotion to the shadow cabinet as shadow education secretary, dramatically raising her profile at Westminster.

Nevertheless, when she stood successfully for deputy leadership following Labour’s crushing defeat in the 2019 general election, she insisted she was “not a Corbynite”.

Despite her distancing from the left, her relationship with Sir Keir, who won the leadership, was not always an easy one.

It reached its nadir following the 2021 local council elections, when he removed her as party chairwoman only to hand her a series of new roles and the title of shadow first secretary of state – effectively shadow deputy prime minister – when she fought back.

As the party’s fortunes picked up, so relations between the pair began to improve, her brash outspokenness a useful antidote to her more buttoned-up leader – “I overshare … but I’ve always said Keir undershares,” she joked.

That outspokenness landed her in hot water when she described the Conservative government of Boris Johnson as a “vile, nasty Etonian … piece of scum”.

She initially defended her comments, only to issue an unreserved apology in the wake of the murder of the Tory MP Sir David Amess, which prompted her to reflect on the abuse that “all too often” characterised political debate.

She herself was the target of newspaper claims that she would cross and uncross her legs to distract Mr Johnson when she stood in for Sir Keir at Prime Minister’s Questions – a report which she dismissed as a “perverted smear”.

Disclosures about the sale of a council house in 2015 in an unauthorised biography by Conservative peer Lord Ashcroft led to a police investigation after the Tories complained she may have broken electoral law and dodged capital gains tax.

After Greater Manchester Police announced – just days into the election campaign – that they would be taking no further action, Sir Keir said she had been fully vindicated, while she said it had all been an attempt by the Conservatives to “clip my wings”.

Freed from the shackles of the police inquiry, however, her first intervention was hardly helpful to her leader, effectively scuppering his efforts to steer veteran left-winger Diane Abbott into retirement.

She was used relatively sparingly in the central election campaign – spending much of the time on her battlebus touring the country – as Sir Keir and Ms Reeves sought to reassure businesses that they have nothing to fear from an incoming Labour government.

But as she prepares to implement the new administration’s workplace reform agenda, that is unlikely to mean she will be taking a back seat any time soon.

As she told the Guardian a dozen years ago, when she was still an up-and-coming trade unionist, people under-estimate her at their peril.

“I’m a pretty young woman, lots of red hair, and everyone expects me to be stupid when I walk into a meeting for the first time,” she said.

“I’m not stupid and most people know that now, but I still like to be under-estimated because it gives me an edge. It gives me a bit of stealth.”