May will give his first TV interview alongside his wife on The One Show but who is the man the PM relies on for her most critical decisions?

The perfect prime ministerial consort, Denis Thatcher is once said to have remarked, is someone who is “always present, never there”. It is a maxim to which Philip May, Thatcher’s sole successor as a male spouse in Downing Street, has been happy to observe since his wife, Theresa, became prime minister in July.

Loyal, ever-supportive but unfailingly discreet, May has stayed out of the limelight since moving to No 10. Photo opportunities have been largely avoided, interviews unfailingly declined.

Until now, that is. On Tuesday evening both the Mays will appear together on the sofa of BBC1’s The One Show, in Mr May’s first broadcast interview.

Theresa May’s decision to call an early general election may have been urged by senior cabinet colleagues and close advisers, but it was only after tramping the paths of Snowdonia with her husband of 37 years over Easter that the decision was taken.

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So who is the man on whom the prime minister relies for her most critical decision-making? The couple have been constant companions since they met at Oxford in the late 1970s, introduced by their contemporary Benazir Bhutto, the future prime minister of Pakistan, at a Conservative Association disco.

Theresa Brasier, a clergyman’s daughter, was then a final-year geography student while Philip May, two years behind her studying history, was the son of a shoe sales rep from Wirral. Though they were both committed Conservatives, it was he who was seen as the rising political star, having won a debating competition for new students at the Oxford Union (he would go on to be elected union president in 1979). They married in September 1980 when Philip was 22 and Theresa 23.

Mrs May took a job in the Bank of England on leaving university; her husband was to follow her to the City, where in the noisy Thatcherite yuppie era he stood out as a quiet and conscientious hard worker, according to contemporaries.

The couple’s close connection was forged more deeply when, shortly after their marriage, May’s father, Hubert, was killed in a car crash; her mother died the following year. Her husband was “a real rock”, she has said – their connection perhaps even closer because she has no siblings.

Facebook Twitter Pinterest Theresa May in the Swiss Alps with Philip. The couple have a shared love of walking. Photograph: Marco Bertorello/PA

“Being an only child,” the prime minister has said, “you don’t feel the same need to be in a big group … But I think it’s good for all of us if there’s somebody else there who you can rely on and who you can sort of share.”

The young couple were, and have remained, deeply committed to the Tory party, taking part in, and seemingly enjoying, every aspect of constituency life. Philip May would go on to become constituency chairman in Wimbledon, but it was his wife who stood for office, first as a councillor in Merton, then unsuccessfully in a number of parliamentary constituencies before securing the nomination for the safe seat of Maidenhead in 1997.

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There was no “deal” between them, she has said, that he should stand back and let her run, but “he’s politically interested, which is a huge advantage – it means he understands campaigning and things like that”.

As Theresa’s political career progressed, so did Philip’s in the City – moving from Prudential, where he invested pension funds, to Deutsche Asset Management and finally becoming a relationship manager at the US investment fund Capital Group.

Despite his own busy career, he has remained a constant presence by her side, including at the village fetes and fun runs May has continued to support in her constituency even since becoming home secretary and later PM. The president of the local constituency association has even described the couple as “two for the price of one”, saying Philip is as devoted to constituency business as his wife. In the run-up to the Copeland byelection in February, Philip May could frequently be found at Conservative central office canvassing voters by phone to urge them to support the (eventually successful) Conservative candidate.

Perhaps unsurprisingly, the longtime couple have developed the same interests – walking, attending their local church (where Philip is one of the servers at holy communion), home-cooked dinners at their constituency home at the weekends (she cooks), watching TV.

Mr May has not greatly enjoyed the increased attention since moving into Downing Street, his wife has said, but relishes attending social events with her – “He always says he gets 90% of the fun for only 10% of the effort.” Aside from helping her to take big decisions, he also advises her on everything from key speeches to her fashion choices – Mr May is apparently “particularly good at choosing handbags”.

And yet, she has said: “He very much takes the view that he supports me in everything that I do but he also understands, when it comes to aspects of the job, it’s for me to get on with, and I have advisers and people around me.”