Philip May is so good at not making himself the story that he seldom appears on the front page of a newspaper, except in photographs of a smiling but uncommunicative figure beside, or slightly behind, the Prime Minister.

He will have been pained by last Sunday’s front-page headline, “Philip May enters No 10 Brexit civil war.” The Sunday Times reported that Gavin Barwell, the Number Ten chief of staff, had accused the Prime Minister’s husband of thwarting a plan to get a cross-party deal with Labour MPs for a Customs Union with the EU.

One source said Barwell “took a pop at Philip May”, while another said, “Philip May was flamed by Barwell for scuppering the outreach to Labour.”

The story was a sign of the extreme pressure inside Number Ten as the Prime Minister and her advisers considered whether to go for Conservative and DUP support, or for a deal with Labour MPs which would infuriate many Conservatives.

In such an argument, Philip May’s instinct would be to preserve Conservative unity. For as one who knows him says, he is “very much a history buff”, well aware that ever since 1846, when Peel split and almost destroyed the Conservative Party, the duty of the Conservative leader is to keep the party together.

With Philip and Theresa May, this is not just a theoretical point. It springs from a tradition of practice. They are Conservative activists who since the 1970s have devoted enormous amounts of time to the generally unsung voluntary side of the party, and to this day do far more canvassing than might be expected when one considers their other commitments.

They could have indicated, in a self-important way, “We have better things to do than knock on doors.” But one of Philip’s characteristics is, as a Cabinet minister puts it, that “although very well-dressed, he is not in the least grand – there’s no side about him”.

The Mays met at Oxford in the autumn of 1976, when Philip arrived at Lincoln College, Oxford, to read History. According to one of his more laid-back contemporaries, in those days “he was blatantly pushy”.

He soon made his mark at the Union, of which in his last term he was elected President, between Alan Duncan, now a Foreign Office minister, and Michael Crick of Channel 4 News.

But although Philip was ambitious, his speeches impressed by their solidity rather than their brilliance. Many undergraduates showed off in a sub-Brideshead manner. He didn’t.

He was born in Norwich and brought up in the Wirral, where he attended Calday Grange Grammar School, founded in 1636. As he related while appearing along with his wife on The One Show during the 2017 general election campaign, his father was a shoe salesman:

“Yes, he worked for a footwear company for the whole of his career in fact. People did in those days. He joined the same company in the late 1940s and went on doing that until the 1980s when he retired.”

Here is a long-term commitment accepted as natural, though no longer fashionable.

Almost as soon as Philip reached Oxford, he met Theresa Brasier, who is 11 months older than him, and in 1974 had gone up to St Hugh’s College to read Geography.

They were introduced to each other by Benazir Bhutto at an Oxford University Conservative Association disco; were married in September 1980 by her father, the Reverend Hubert Brasier; and have remained – as everyone who knows them attests, and as can be seen when one watches the interview quoted above – deeply in love.

They are Anglicans, and on Sunday mornings can be found worshipping at St Andrew’s, Sonning, on the Thames just outside Reading.

While fulfilling this regular commitment, they are often photographed but seldom talk. They just do it.

They supposed when they married they would have children, but the children did not come, and again they do not talk much about this.

Her parents died soon the wedding. Philip became, and has remained, her “rock”. Although their contemporaries thought he was more likely to go into politics than she was, it happened the other way round.

They both took jobs in the City, he at the brokers de Zoete & Bevan, she at the Bank of England. They bought a house in Wimbledon and got involved in local politics. He was made chairman of Durnsford Ward, where she was the Conservative candidate and in 1986 narrowly defeated Labour to gain a seat on Merton Council.

In 1990, Philip became chairman of Wimbledon Conservative Association, where Oliver Colvile, then the local agent, recalls – as Rosa Prince relates in her life of Theresa May – that during the 1992 general election,

“Despite his very demanding City job, Philip took his job as one of my bosses very seriously. We used to speak at least a couple of times a day. When I made the occasional mistake he would dismiss it is ‘fog of war, dear boy, fog of war’.”

Colvile went on to become MP for Plymouth Sutton & Devonport, but lost his seat at the 2017 general election.

In 1989 Theresa won was selected as the candidate in Durham North West, a safe Labour seat. She and Philip spent the two and a half years leading up to the 1992 election travelling between Wimbledon and Durham, often taking friends up for the weekend to stay in the house they had bought in the village of Lanchester.

Rather unusually, she opted to do no hustings with the sitting MP – something the underdog is usually keen to do, in order to become better known.

Her method was to get out the Tory vote by meeting Tory voters in their houses, along with those neighbours the Tories reckoned might be receptive. Already she possessed a strong disinclination to stage a performance for the benefit of the wider public.

Philip was the trailing spouse, but did not opt out. A pattern of loyal support was already in place, which continued once she had been elected in 1997 for the safe Tory seat of Maidenhead.

“Who are the Mayites?” people sometimes ask. The answer is that the main one is called Philip.

He was one of the few men who turned up to the meetings held for the spouses of Conservative MPs. The wife of a Tory MP recalls that Philip was “treated as a precious object” because he was so unusual.

A friend who has known him since Oxford says:

“He’s an extremely shrewd, thoughtful, rather gentle man. He’s politically very alert. He knows where people are coming from when they come into a room.

“He never ever imposes his views on others. He behaves rather gently with other people’s sensibilities. He doesn’t crash around.

“They’re very close. They were already very close at Oxford.  They have very little of the ambitious restlessness that is often associated with senior politicians.”

Theresa uses Philip as a sounding board for her major speeches and major decisions. It is impossible for an outsider to know whether, as I would guess, he confirms what she has already decided to do, or changes her mind.

Chris Wilkins, who wrote speeches for her and was her Director of Strategy, recently described, in a podcast with Anushka Asthana of The Guardian, how he and three other senior advisers including Nick Timothy set about persuading her to call the 2017 general election.

Philip was the most resistant to their case:

“He definitely had the largest reservations of anyone in the room. His point really that he made was that while he could understand all the arguments we were making, we also had to understand what a big risk it was for them as a couple, and he said we had to appreciate that it had taken them years to get to the position of being in Number Ten, and we were asking them to put that all at risk.”

The Prime Minister nevertheless went ahead and called the election, and Philip was there to support her when she discovered to her horror that it left her in a weaker parliamentary position.

On the great question of Brexit, Philip like her was a quiet Remainer. He would be averse to the risk of leaving without a deal, but would be even more alarmed by the idea of taking any course of action which risked breaking the Tory Party into fragments, with anarchy or a Corbyn government the likely consequence.

His greatest influence is probably not on questions of policy, but on her whole style of politics. Philip possesses a quiet wit, and generally knows how to bring a smile to her face.

She herself has said he is very good at knowing when to bring her a cup of tea – perhaps the most uncontentious of all ways in which an English person can demonstrate sympathy and support. Whisky, beans on toast and flowers are also deployed when the appetite for them is discerned.

Like her, he feels an instinctive distaste for the look-at-me-I’m-great style of politics. To him, that would seem bogus. To the British press, this refusal to draw attention to herself by saying interesting things seems wilfully dull.

The large section of the British public which values respectability above originality probably sides with Philip. She herself said, when interviewed by James Cleverly for The House: “I’m not a stand-up comedian. I am Prime Minister.”

When Cleverly ventured to ask her what role her husband plays in her decision making, she bridled:

“I just wondered when you asked me about Philip’s role, whether if I was a male Prime Minister, you would have asked the same question about their wife?”

The answer is that it is still easier, if she chooses to play it that way, for a wife to opt out of that side of things.

But when the pressure is on, any spouse is in danger of getting drawn in, and decades of carefully avoiding the limelight may be set at naught.

Another Oxford friend – a devout Leaver, so inclined at this fraught moment in our island story to be suspicious of Remainers – says of the Prime Minister’s husband:

“Philip is politically combative and not terribly subtle. At certain points he will say, ‘You fight them darling’.”