Hypocrisy is very much alive and well in the City of London. In public, firms say they encourage DEI (diversity, equity and inclusion, or EDI — equality, diversity and inclusion).

Yet a recent Stonewall study had some pretty shocking discoveries: two in five LGBTQ+ employees still feel the need to hide the fact they are LGBTQ+ at work and 12 per cent of LGBTQ+ employees believe they have been fired or dismissed because they are LGBTQ+. It goes on — and makes for very ugly reading.

Nearly a third of LGBTQ+ employees did not agree they could be themselves at work. Of these, more than half have experienced discrimination, such as receiving verbal or physical abuse, or feeling excluded. Three in 10 LGBTQ+ employees wouldn’t feel comfortable reporting discrimination if they experienced homophobic or biphobic bullying or harassment.

This is shaming stuff, made worse because it’s set against a backdrop of businesses and City firms proclaiming their pro-diversity and inclusivity policies. Some have rolled back their DEI programmes to appease Donald Trump’s administration but most still make a virtue of their enlightened approach.

Another study, from Pride in Leadership, found that 85 per cent of LGBTQ+ professionals had encountered career obstacles due to their identity. These ranged from being passed over for promotions and a lack of LGBTQ+ representation in leadership, to verbal and even physical abuse at work.

In City offices there is what’s known as “don’t ask, don’t tell” when it comes to homosexuality.

On macho trading floors it doesn’t pay to be gay. Teasing or being overlooked for promotion may follow. Worse, it could result in dismissal — not on the grounds of being gay, that would be illegal, but another reason will be concocted. Best to play shtum and pretend you’re straight.

It’s a silence that is vividly described in a new book from Britain’s first openly gay business leader. He is Michael Bishop, now Lord Glendonbrook, and formerly owner of what was once Britain’s second-biggest airline, British Midland.

Bishop, who sold British Midland, then known as bmi, to Lufthansa in 2009, was also chair of Channel 4. In his new autobiography, Lessons from a High Flyer, he describes the torment of a gay man having to live a lie.

It was only in 2002, when he owned the airline and felt he no longer had anything to lose and nobody to answer to, that he was confident enough to go public.

His anxiety was based on decades of terror, knowing that if he was found to be gay his job could end, or worse.

Bishop had realised he was gay in his teens, “but that it also had to be hidden”. Back then, homosexuality was illegal.

In 1972, Bishop had been made managing director of British Midland. The then chairman entered his office. “‘I need to ask you something,’ he said. ‘People here, say you’re queer. Is this right?’ I replied that no, I wasn’t. ‘Good, because if you’d said yes I have your resignation letter right here,’ he replied, pointing to his jacket pocket.

“Externally, I was calm; internally, I was seething with a mixture of anger and humiliation. There I was, the boss, on the point of being sacked because of my sexuality. I’m not prone to violence but I really did want to hit him. How dare he? How could he be so arrogant and trumped-up? What possessed him to loathe his fellow man, as he clearly did, if they happened to not be the same as him. It was outrageous.”

Scared of the stigma, of getting caught, “I went along, as we were almost forced to... having ‘girlfriends’, trying to fit in; I was anxious to be accepted. It was a farce of course, a complete deceit.

But there was no other way — if you wanted to get on, to advance your career, to be socially included… you had to be hetero or at least behave as though you were.”

It was “belittling and shaming, leading a double life, possessing a certainty you were never allowed to express, not in public anyway. It’s difficult to image the effect that has, of hiding, forced to be something you’re not, having to take great care, living in permanent fear of being outed. The more successful I became, too, there was always the anxiety of blackmail, perhaps not in financial terms, but of my ‘secret’ being exploited by someone to advance their career. It was a permanent, never-ending nagging worry.”

He worked, too, in an industry that was heavily male-dominated.

“Those who reached the top were men and they tended to be a certain sort of man. Bluff, confident, alpha males. That did not leave room for being ‘different’. By and large, they liked sports and cars and drinking and girls.”

As a result, “You conformed and that was it. Anyone who stood out as not being the same, not interested in the same things, not talking the talk, was literally apart… You kept your head down and remained quiet.”

Bishop always made sure that when he attended work events he was accompanied by a woman — a colleague, a friend. Nevertheless, he’d not married, not had an obvious girlfriend and people suspected. The media used words like “dapper” or “elegant” ostensibly to describe his smart dress sense but he regarded it as code for gay.

The late Lord King, his arch-rival at British Airways, described him as “that cute little brute”. He doubts whether King would have spoken of him in such terms if he was straight.

Once, The Sun newspaper called his house. Martin, his long-term partner, later his husband, was at home and a reporter asked: “Is there any truth in the rumour that Michael is having a homosexual relationship with Richard Branson?”

At that time, in the early 1990s, Bishop’s British Midland, Branson’s Virgin and King’s BA were embroiled in fierce competition. Finally, in 2002, Bishop came out. Before then, no comparable senior business figure in the UK had dared to go public with their homosexuality.

Says Bishop: “I took the view there was nothing to be gained by denying it anymore. I owned the company; there was no one above me. It was not as if my career would suffer as a result.”

He thought those close to him must have known.

“Garry, my long-serving driver, certainly knew, given the conversations he’d heard, the places he’d taken me and the people he’d met. Rosemary, my PA, absolutely knew. In truth, they all did, as did members of my family and media.”

He gave an interview to The Sunday Times and was asked the question. That in itself was not unique — he’d been asked before and batted it away, fudged or denied. “I could have done the same again. I could have said no, I was not homosexual. This time, I deliberately chose not to. I had nothing to lose, not anymore. In doing so, I was the first leading British businessman to proclaim they were homosexual.”

Bishop was asked by the paper if being gay had ever been an issue for him in business. “Not to me, no,” he replied. The interviewer noted how he seemed uncomfortable. There was still prejudice, he said. It was responsible, he added, for explaining why he had so few friends in the industry. “Lots of people have social friendships integrated with their business, that’s something I’ve never done… I think you develop a different kind of social life.”

He didn’t exactly open the floodgates. Charles Allen at ITV and John Browne from BP followed him and after them a few others, but that’s it.

“There have been more since,” says Bishop, “but the number remains pitifully low and nowhere near what the proportion of gays and lesbians in society suggest it ought to be.”

It’s appalling, he says, that someone’s sexuality should still be counted against them today. Dreadful too that they “should feel repressed, unable to be who they are — that is wrong, unnatural, and stifles their positivity and creativity”.

Bishop ends on a positive note: “We’ve still far to go, but hopefully I’ve helped.” He has — but he is also right to say, as shown so clearly in the Stonewall study, there is much to be done.

Lessons from a High Flyer by Michael Bishop is out now (Unicorn, £25)