The prime minister's obduracy is on full display as she heads fighting into a Conservative party confidence vote late Wednesday that will define not just her own future as leader, but Britain's Brexit destiny too.

The Oxford-educated daughter of a vicar said she would contest the vote among Conservative members of parliament, forced by a number of dissident MPs, "with everything I've got".

It was a typically defiant performance delivered outside 10 Downing Street, which she took over after her predecessor David Cameron walked out, hours after voters opted in June 2016 for Britain to exit the European Union.

May herself campaigned in the referendum to remain in the EU. But she has since fought tenaciously to implement the voters' verdict against resistance from both those who think it was a terrible mistake, and the hardliners who want a clean break with the EU.

She compares herself to her cricketing hero Geoffrey Boycott, who was a byword for doggedness as a batsman, and gleefully seized on the "bloody difficult" put-down delivered by party elder Kenneth Clarke.

But May's perseverance has also been characterised as intransigence, not least in her adoption of inflexible "red lines" in the Brexit negotiations that critics say has led to the current impasse.

She eschews gossip and networking, proving herself through hard work, spending six years in the tough job of home secretary (interior minister) before succeeding Cameron.

Her reserved nature often makes for stilted relations with world leaders and voters. Her style of repeating the same phrases and avoiding direct questions has earned her another nickname in the media -- "Maybot".