Theresa May’s promise to stand down ensures her legacy will be defined by Brexit

The timing of Theresa May’s departure as Prime Minister means that her legacy will be defined by Brexit.

She arrived in Downing Street on July 13 2016 faced with the task of bringing together party and country after the traumas of the EU referendum.

But her entire premiership was dominated by tortuous negotiations in Brussels and vicious infighting within her own party over the terms on which the UK would leave.

Mrs May, 62, marked her arrival with an impassioned promise on the steps of Number 10 to tackle the “burning injustices” which hold back the poor, ethnic minorities, women and the working classes in modern British society.

But her disastrous decision the following year to hold a snap election deprived her of her slim majority in the House of Commons, leaving her dependent on the Democratic Unionist Party.

From that point, she was engaged in a day-by-day battle to force her agenda through and maintain the fragile unity of her Government.

She lost more than 30 ministers – most of them quitting over her Brexit plans – saw her keynote policy defeated by a record-breaking 230 votes and suffered the indignity of having her Government found in contempt of Parliament.

It all looked so different when Leave-backing leadership rival Andrea Leadsom dropped out of the contest to succeed David Cameron, clearing the way for the former Remainer to take office without a vote of Tory members.

Hailed by the press as a “new Iron Lady”, the vicar’s daughter hardened by six years as home secretary immediately showed her ruthless streak, sacking both Michael Gove and chancellor George Osborne, with whom she had clashed in Cabinet.

In her first speech to Conservative conference, she shocked many by setting out “red lines” for withdrawal which put Britain on track for the hardest possible Brexit.

She dismissed her critics as people who saw themselves as “citizens of the world” but were in fact “citizens of nowhere”.

Determined to show she was taking the UK into a new global role, she rushed to be the first world leader to meet Donald Trump at the White House after his inauguration in January 2017.

But footage of her holding hands with the US president exposed her to ridicule back home and raised questions about her closeness to a man whose unpredictability was already causing concern in capitals around the world.

The fateful decision to call an early election, in the hope of securing the comfortable majority she needed to implement her Brexit plans, was taken on an Easter walking holiday in Snowdonia with husband Philip.

A poorly received manifesto and hastily withdrawn social care policy, coupled with a robotic campaigning style and the surprise outbreak of Corbynmania, saw her squander a 20-point lead in the polls and lose 13 MPs.

The result saw the Tory majority wiped out while a visibly distraught Mrs May had to turn to the DUP to prop her up in Parliament, with £1 billion in extra Government funds going to Northern Ireland.

That year’s conference in Manchester ended in humiliation, as she was handed a P45 by a comedian on stage, lost her voice to a persistent cough and ended her speech with letters falling off the backdrop behind her.

In December, she seemed to salvage the Brexit deal, finalising a Withdrawal Agreement with European Commission president Jean-Claude Juncker after a pre-dawn flight to Brussels.

But that agreement contained the seeds of future troubles, introducing the controversial “backstop” customs arrangements for Northern Ireland which were to be fiercely opposed by the DUP and hardline Tory Brexiteers in the European Research Group.

Her attempt to unify her Cabinet behind her deal at Chequers in July 2018 led foreign secretary Boris Johnson and Brexit secretary David Davis to walk out of the Government.

They were followed in November by Mr Davis’s successor Dominic Raab and other Leave-backing ministers, who quit in protest at the final deal agreed with leaders of the other 27 EU states in Brussels.

Meanwhile, Mr Trump’s summer visit to the UK only deepened her woes, as he said her Government was in “turmoil” and that Mr Johnson “has what it takes” to be PM, only to blithely shrug his comments off as she gritted her teeth alongside him at a sun-drenched Chequers press conference.

By the winter, Mrs May was in open warfare with the DUP and many of her own backbenchers, who said her deal would leave the UK in a state of “vassalage”.

She survived no-confidence motions from her own MPs and Labour’s Jeremy Corbyn, but was forced to postpone the key “meaningful vote” ratifying her Brexit deal when it became clear she was heading for defeat.

When the deal was finally put to a vote in January this year, it was crushed by the largest majority in modern parliamentary history.

And it fared little better when it returned in March, defeated by 149 votes with scores of Tories rebelling.

It remains to be seen whether her decision to offer the ultimate political sacrifice will be enough to seal the deal at the third attempt and secure her legacy as the PM who delivered Brexit.