The man holding the Brexit cards: Speaker John Bercow

LONDON,

As Prime Minister Theresa May grapples with parliament to get her way on Brexit, one man stands at the centre of it all with the power to shape what happens next.

House of Commons Speaker John Bercow, who on Monday scuppered the government's plans to hold another vote on a divorce deal already rejected by parliament, is playing a pivotal role in the Brexit endgame.

Bercow is best known for presiding over debates, bellowing "Order! Order!" at unruly lawmakers and chastising ministers who displease him.

Citing hundreds of years of precedent, the speaker told parliament on Monday that the government cannot resubmit the same deal agreed with the EU last year for another vote.

It was the latest instance in which Bercow showed he is willing to intervene forcefully against the government in his drive to give parliament a greater say on Brexit, an issue that has sharply divided the country since Britons voted in 2016 to leave the EU.

BIAS ACCUSATIONS

Bercow was first elected as an MP for May's Conservative party, but his elevation to speaker in 2009 means that he is supposed to be politically neutral.

However, his interventions in Brexit debates have prompted accusations from his former colleagues that he is biased both against the government and Brexit itself.

Opposition Labour MPs instead broadly support him.

He has also been accused of presiding over a culture of bullying in the Commons, and did not deny he once referred to a senior female government minister as "stupid".

BITTER ROWS

Exchanges between MPs and the speaker have become increasingly bad-tempered, with tensions reaching boiling point in January, when — defying precedent and the advice of his clerks — Bercow allowed MPs to amend a government motion on May's deal.

The effect was to force the prime minister to quickly return to the Commons to explain herself if the agreement was rejected by MPs — as it was a few days later.

Bercow's decision sparked an angry row in the chamber, as Conservative MPs and ministers stood up to denounce him to his face.

"Many of us will now have an unshakeable conviction that the referee of our affairs... is no longer neutral," one said.

Another challenged him over a sticker spotted in the car he drives, saying "Bollocks to Brexit".

Bercow replied tersely that it belonged to his wife and "she is entitled to her views", and insisted he was only standing up for the rights of individual lawmakers.

Asked about whether he had ignored the advice of his aides, he said: "If we were guided only by precedent, manifestly nothing in our procedures would ever change."

CONSERVATIVE VIEWS

Born in 1963 into a modest family, Bercow grew up in London and was a child tennis champion, leading to a lifelong love of the sport.

He was always a Conservative, but in his youth held far-right views that he has now rejected.

He became an MP in 1997 and 12 years later was elected as Speaker, becoming the youngest person to hold the role for 100 years.

Bercow has sought to modernise parliament, abandoning the Speaker's traditional robes for a simple gown over a suit, and seeking to make it easier for female MPs with new babies.

But critics say he is pompous, and overfond of the sound of his own voice.

One Conservative MP famously described him as a "stupid, sanctimonious dwarf".

Before the recent Brexit clashes, he also enraged many Conservatives with his outspoken opposition to allowing US President Donald Trump to address parliament.

He is due to retire in the next year, but there have been suggestions he could stay on to see the Brexit process through -- an idea likely to dismay the government.

Given Bercow's support from the opposition, ministers can do little about it although reports suggest they might deny him a seat in the House of Lords when he steps down as punishment.