Theresa May had a mission to fight Britain's "burning injustices" through strong and stable leadership ─ but her legacy as prime minister will be anything but.

The Conservative premier's turbulent time in office was swamped and ultimately sunk by her legacy-defining battle to secure a Brexit divorce deal.

It eroded her authority and led to her announce last month that would step down as leader of her party on June 7. She will remain as Britain's prime minister until her successor takes over.

May's last major act before starting the leadership contest was to welcome US President Donald Trump, with whom she had an up-and-down relationship, on a state visit to Britain.

Symbolic of May's diminished authority, the US leader joked with leadership candidates about who would replace her while she stood beside him at a press conference.

Why May couldn't muster support

May won praise for her determination and ability to survive a rolling three-year political crisis since the referendum vote to leave the European Union.

But her approach to the Brexit endgame, refusing to accept MPs' trenchant opposition to her deal before belatedly opening ultimately futile negotiations with the Labour main opposition, left May politically adrift.

In a forlorn bid in March to appease the most ardent eurosceptic MPs in her party, May, 62, offered to resign if they finally approved her deal.

But several dozen rebelled anyway, consigning it to a third defeat in parliament and leaving her premiership mortally weakened.

She was forced by her party to agree to set out a timetable for her departure, but asked for time to give lawmakers a fourth chance to vote on the agreement in early June.

However, her own MPs' patience ran out and May was forced last month to name the date of her departure, triggering the fevered leadership race to replace her.

“She has failed,” said Simon Usherwood, from the University of Surrey's politics department. “There's very little to commend her. She doesn't really have a legacy”.

'Goody two shoes'

The daughter of a Church of England vicar, May was born on October 1, 1956 in Eastbourne ─ a seaside town in southern England where her father was a chaplain at the local hospital.

She has described herself in interviews as a “goody two shoes” whose Protestant faith defined her upbringing.

She listened to cricket matches on the radio with her father and knew that she wanted to become a politician when she was just 12.

May studied geography and met her husband Philip at Oxford University before joining the Bank of England.

The two never had children and May devoted herself to a life of public service that saw her become Conservative Party chairwoman in 2002.

May made her first splash by telling their annual conference to change the Conservatives' image as “the nasty party” if they wanted to unseat then-popular Labour premier Tony Blair.

But a 2010-16 stint as home secretary saw May adopt isolationist rhetoric that included a vow to create “a really hostile environment for illegal migration”.

'Maybot'

She became prime minister in the aftermath of the 2016 Brexit referendum which swept away her predecessor David Cameron.

She took office pledging to fight the “burning injustices” in British society, but made little headway as her entire premiership became dominated by the Brexit drama.

Despite having made a cautious case to stay in the EU, May embraced the cause with the mantra “Brexit means Brexit”.

Her promise to leave the EU's institutions and end free movement of workers delighted eurosceptic MPs, but caused dismay among many pro-Europeans.

The splits in her Conservative Party became a serious problem after a disastrous snap election in June 2017, when she lost her parliamentary majority.

May was forced to strike a deal for support with Northern Ireland's pro-Brexit Democratic Unionist Party, and since then has struggled to keep her party and its allies together.

Naturally reserved and reliant on her husband and a few close aides, she often says she is just quietly “getting on with the job”.

But in the 2017 election, the leader struggled to engage with voters and was dubbed the “Maybot” after churning out the same answers and “strong and stable” soundbytes over and over again.

'Closed' style

May was written off several times before announcing on May 24 that she would step down.

Columnist Matthew Parris ─ a former Conservative MP ─ called her the “zombie prime minister” for her ability to stagger on despite multiple attacks.

She survived a no-confidence vote, the resignations of a string of high-profile Brexit supporters, notably former foreign secretary Boris Johnson, and has endured constant sniping from MPs on the sidelines.

But ultimately her closed style of leadership and Brexit gridlock in parliament doomed her premiership.

“It's hard to think of a Tory politician who would have been the perfect PM in such circumstances,” Tim Bale, politics professor at Queen Mary University of London, told AFP.

“But it's just as hard to think of anyone who would have been much worse than her.”