Theresa May’s legacy as Prime Minister will be defined by her fateful decision to call a snap election – and the Brexit chaos that followed.

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.

She will be leaving with her party fractured and the country still divided over Europe.

Her premiership has been dominated by tortuous negotiations in Brussels and vicious infighting within Tory ranks 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.

Theresa May becomes PM
Theresa May arrives at Downing Street after being appointed prime minister (Stefan Rousseau/PA)

But her disasterous 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 (DUP).

From that point on, 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 former Remainer Mrs May to take office without a vote of Tory members.

Hailed by some commentators 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 a hard 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 and raised questions about her closeness to a man whose unpredictability was already causing concern in capitals around the world.

Mrs May's awkward demeanour and endlessly repeated 'strong and stable' mantra saw her dubbed the Maybot during the 2017 election campaign
Mrs May’s awkward demeanour and endlessly repeated ‘strong and stable’ mantra saw her dubbed the Maybot during the 2017 election campaign (Danny Lawson/PA)

The 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 a surprise outbreak of Corbynmania, saw her squander a 20-point lead in the polls and lose 13 MPs.

When the dust had settled her Tory majority had been wiped out and 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 in return.

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.

Comedian Simon Brodkin interrupted Mrs May's disastrous conference speech in Manchester
Comedian Simon Brodkin interrupted Mrs May’s disastrous conference speech in Manchester (Peter Byrne/PA)

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.

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.

Trump
There were awkward moments for Theresa May during Donald Trump’s visit to the UK in 2018 (Stefan Rousseau/PA)

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, and more unhappiness in the ranks as another extension was sought.

POLITICS Brexit
(PA Graphics)

A third vote on the original Brexit date of March 29 was prefaced by a promise from Mrs May to quit if the deal passed, but even that was not enough to secure victory and the Government was again defeated, this time by 58 votes.

There was Tory mutiny as it became clear the UK would have to go through EU elections on May 23 and the Prime Minister faced mounting calls to immediately set out her departure timetable.

Chairman of the 1922 backbenchers’ committee, Sir Graham Brady, threw the beleaguered leader a lifeline by allowing her extra time to strike a deal with Labour and hold another vote before setting out a schedule.

Brexit
Prime Minister Theresa May and Labour leader Jeremy Corbyn (PA)

However, putting her future into the hands of Jeremy Corbyn failed too and talks with Labour collapsed on May 17.

With a fourth vote pencilled in for the first week in June, Mrs May made a last-ditch plea for compromise on Tuesday, but her plan was pronounced dead on arrival.

Mrs May was left to face down hostile MPs in the Commons on Wednesday as a flurry of no-confidence letters were publicly handed over to Sir Graham.

With MPs from all sides rejecting her fourth attempt at reaching agreement before it even reached a vote, the ship of her Brexit compromise deal appeared holed beneath the waterline and about to take down Mrs May too.

Mrs Leadsom resigned as Leader of the House of Commons on Wednesday night and other key ministers made clear their disquiet with the new Brexit plan.

European Parliament election
Theresa May and her husband Philip arrive to cast their votes at a polling station near her Maidenhead constituency (Victoria Jones/PA)

By the time Mrs May left Downing Street to vote in the European Parliament elections on Thursday, proposals to publish her latest Withdrawal Agreement Bill had been postponed.

And with her party facing a drubbing in those elections, an announcement about her final departure from Downing Street became inevitable.