Some say the prime minister is resilient, others that she is inflexible, but all agree she is determined in her mission

Supporters of Theresa May put her extraordinary inflexibility in the face of new facts down to two things: her fabled resilience, and her deeply ingrained determination not to split the Conservative party.

Chris Wilkins, who worked for the prime minister in Downing Street, including drafting key speeches, says: “I often reflect on my time there and think I underestimated the extent to which she is a dyed-in-the-wool Conservative. She is absolutely steeped in the party.”

When Jacob Rees-Mogg invoked the Victorian prime minister Robert Peel last year to warn May against relying on Labour votes to pass her Brexit deal, he knew the analogy would hit home. Peel split his party over the corn laws, and banished them from power for a generation as a result.

Wilkins says May is also sustained by a sense that she is the only grown-up in the room; a serious politician executing what she repeatedly calls “the will of the people”, rather than posturing like the former public schoolboys she trounced in the Tory leadership race.

“She has this phrase: ‘Politics is not a game.’ That is the Theresa May worldview,” he says.

Play Video 2:43 ‘This is the time to put self-interest aside’: May in Brexit plea outside No 10 – video

As the prime minister herself put it during her leadership speech: “I don’t tour the television studios. I don’t gossip about people over lunch. I don’t go drinking in parliament’s bars. I don’t often wear my heart on my sleeve. I just get on with the job in front of me.”

Less charitable colleagues argue that this belief in her personal fitness to understand, and deliver, what the public wants is itself a kind of vanity.

Aside from the august institution that is the Tory party, and the “precious union”, as she calls it, it can be hard to say what May believes in. Her former chief of staff Nick Timothy was an enthusiastic advocate of a kind of red Toryism.

But the departure of “the chiefs” – Timothy and Fiona Hill – was one of the few things that did change after the general election, and that theme has been all but swamped by Brexit.

However, one thread running consistently through May’s tenure as home secretary under David Cameron, and her premiership, has been controlling immigration.

Unlike the former chancellor George Osborne, she was a champion of stricter migration controls. Vince Cable, who was the business secretary in the coalition, has even accused her of being obsessed with hitting the net migration target.

As prime minister she has resisted removing students from the target despite a push from inside her own cabinet, and has put the brakes on visa liberalisation. She firmly believes the public’s view on immigration is more in line with her own than those of the more liberal Tory MPs.

May’s “burning injustices” speech, delivered when she entered Downing Street in the tumultuous summer of 2016, has entered political folklore, not least because she frequently mentions it herself. But another speech, delivered the morning after the general election in 2017, with her grip on power uncertain, was a better guide to the tenor of May’s premiership.

During the election campaign, the prime minister had made a personal plea to the public to back her Brexit strategy by increasing her majority so she could overrule remainers at Westminster.

Far from endorsing her “strong and stable” leadership, the electorate appeared to warm to Jeremy Corbyn during what even her own colleagues acknowledge was a disastrous campaign, and stripped the Tories of their majority.

That morning, speaking outside No 10, May gave not a hint of apology or humility, let alone suggest she would flex her position on Brexit to accommodate the dramatically different parliamentary reality.

Instead, she said she had spoken to the Queen, and would work with the Democratic Unionist party to form “a government that can provide certainty and lead Britain forward at this critical time for our country”.

She then gave a familiar promise to “deliver on the will of the British people by taking this country out of the European Union”, before briskly concluding: “Now let’s get to work.”

Play Video 2:52 ‘Now let’s get to work’: Theresa May’s Downing Street speech in full - video

It was as though “nothing has changed” – which began as her tetchy response to questions about the Tories’ social care policy at a campaign press conference – had become a guiding principle.

These past months have brought together the stubborn grit that is May’s most visible character trait, with that overriding determination not to be the leader who splits the Tories – along with a firm belief that the public wants politicians to “deliver Brexit” and control immigration – and she’s the woman to do it.

So perhaps it should be no surprise that May’s reaction to the resounding rejection of her Brexit deal by MPs from every party was, just like after her general election humiliation, “Now let’s get to work”.