LONDON (Reuters) - In his deep baritone, Geoffrey Cox, British Prime Minister Theresa May’s top lawyer, relishes winning the argument.

FILE PHOTO: Britain's Attorney General Geoffrey Cox addresses Parliament ahead of the vote on May's Brexit deal, in London, Britain, January 15, 2019. UK Parliament/Jessica Taylor/Handout via REUTERS

It’s something that came easily at his top London legal practice but leading her delegation in last-ditch Brexit talks with the European Union could test his skills to the limit.

May and her government have handed Cox the tricky task of securing changes to her deal on leaving the EU that can win the approval of a deeply divided parliament and smooth Britain’s departure, currently scheduled for March 29.

Cox, 58, does not have much time - and if parliament rejects May’s deal again, as it did in January, then Brexit is plunged into deeper uncertainty. But if he is feeling the pressure, Cox has yet to show it.

He has quietly pursued talks with Brussels, shuttling back to update London and sowing the seeds of at least cautious optimism among May’s cabinet of top ministers that the negotiations could be on the cusp of a much-needed breakthrough.

“We are moving in the right direction,” one minister said on condition of anonymity. “If he does manage it, I will make a golden statue of him and bow down to it every morning.”

Quiet is not a word often used to describe Cox, whose trademark booming voice was used to effect at last year’s annual Conservative Party conference, when he raised the otherwise lukewarm temperature among members before May took to the stage.

And that volume, those who speak to him say, rarely decreases, as he approaches even the most routine chats as an exercise in oratory.

It has helped win some major cases, including successfully defending the former premier of the Cayman Islands, McKeeva Bush, but can also irritate other Conservative lawmakers, many of whom share his legal training and bristle at his jibes.

Whether it helps his Brussels quest is yet to be seen. EU officials say Cox is starting from zero and having to learn basic facts about the bloc.

“He has a very steep learning curve ahead of him,” one senior diplomat said, while another said Cox was asking for changes that were rejected months ago.

BACKSTOP BRAVERY

At the heart of the challenge facing Cox is the Irish “backstop”, an insurance policy to ensure no return to a hard border between the British province of Northern Ireland and EU member Ireland after Brexit. Two Brexit ministers resigned last year partly over the backstop issue.

Cox is charged with offering legal assurances to euroskeptic UK lawmakers that the backstop - which would be triggered if a new trading relationship fails to sweep away any need for additional border checks - will not keep the country trapped in the EU’s sphere indefinitely.

For some in the governing Conservative Party, his quest is almost a form of divine justice.

After being forced to reveal the legal advice he gave to the government in parliament in December, it was his assertion that the backstop could entrap Britain that hardened opposition to May’s deal.

He then alienated some lawmakers by telling parliament to “grow up and get real” when he argued that the full legal advice should be withheld to safeguard the public interest. A day later Cox was almost in tears when he became the focus for parliament’s contempt proceedings against the government

Hardline Brexit supporter Bill Cash accused Cox of underestimating “the significance of what we are dealing with here”. Cash will now form a committee of euroskeptic lawyers to judge whether any revised agreement is watertight.

It is a position few would relish, but Cox is dutiful and, like May, an archetypal Conservative in many respects.

In parliament, he represents an arable, prosperous region of southwest England where he lives.

In 2017, he told a young interviewer at the private school where his sons went, that he would have liked to have become a poet but wasn’t good enough. He spoke of his enjoyment of literature, his early interest in politics and his dislike of “kowtowing to a lot of political correct nonsense”.

But perhaps his proudest achievement is his role as a senior lawyer, or Queen’s Counsel, and he will hope to bring his legal knowledge to the talks.

“He wears his brain on his sleeve,” said the minister, adding in answer to whether he could be the Brexit hero? “I hope so.”