In the end it only took a bunch of flowers and a letter saying “I think you’re terrific” to propel the young Diana Henderson into a secret affair. She had been working with her lover for some time and there was mutual attraction but this is what sparked it off.

“Relationships aren’t like a book, that you open the cover and — bang — start reading at chapter one,” she recalls. “But it was fantastic, a wonderful thing to do and it didn’t half do me good.”

This wasn’t a simple fling, though: it was one that could have compromised Henderson’s future with the army because she was conducting a relationship “between ranks”. Now she is director of alumni at Queens’ College, Cambridge, and the former commander of a Territorial Army regiment in the Royal Logistic Corps — but then she was just a young officer making her way up.

Henderson will not reveal any details, including whether her former lover was married, but last week she used a public lecture at Bath University to call on the army to overturn the ban on relationships between superiors and subordinates, arguing that “the whole way people conduct their lives has changed dramatically”.

Hers is a controversial view: can the same social rules about love apply when life-or-death situations are regularly being faced? How can personal relationships between superior and subordinate — and the preferential treatment that could follow — not adversely affect the rest of a tightly knit unit?

“The consequences simply cannot be compared to, say, a sales manager having a fling with a junior member of the sales force,” says Antony Beevor, a former officer with the 11th Hussars and author of Inside the British Army. “All that is at stake in that case is office corridor rumours. In the armed services, the effect can be truly destructive.”

Not that the consequences in business are always that simple — last week Harry Stonecipher, the chief executive of Boeing, was sacked for sending unseemly e-mails to a woman in the company with whom he was having an affair.

But Henderson argues that by simply prohibiting or refusing to even discuss the subject, it merely goes underground and the unspoken reality is that the “between ranks” ban is a snobbish relic of class culture.

Today the Ministry of Defence says there has never been a ban on relationships: it prefers the more polite term “discouragement”. Sanctions that are imposed are purely “administrative”.

But the lurid headlines that the army has endured over the past decade suggest that people have not been discouraged — nor have the consequent sanctions been merely administrative. From “Captain Crumpet” Angela Jackson, who had an affair with Colour Sergeant Brian Taylor, to “Lieutenant Lusty” Joanna Kay, who was sent home from her posting in Northern Ireland after performing a sex act on a sergeant, there have been a succession of scandals.

Heidi Cochrane — a pin-up girl on an army recruitment poster — went absent without leave with a married sergeant. And last year the employment tribunal of Angela McConnell produced jaw-dropping allegations: a major with a dozen mistresses and cavalry officers betting on their chances of sleeping with female recruits.

For Henderson such revelations are the natural consequence of the army being unable to face up to 21st-century life and of expecting 17-year-old recruits to sign up to an existence at odds with their experiences of life outside. “No one is born into the army,” she says. “They come from the background of ordinary life. And suddenly they enter the forces and there is this hiccup where everything to do with relationships is suspended.”

When Henderson joined the Women’s Royal Army Corps in 1966 , a woman’s place was doing the accounts and sitting in offices. “It was extremely frustrating. There were glass ceilings, tokenism, discrimination. I reached the point of being a senior major and being told outright, ‘Don’t even bother thinking about going up a rank, Diana: it will not happen’.”

She did in fact reach the rank of lieutenant-colonel. But she says many women left the army because the prevailing attitude was that they could not have relationships with other soldiers. And if they defied that and were discovered it tended to be the women who paid the price. Those that were not formally dismissed were often bullied and harassed. Conversely, the culture of silence meant some women were pressured into sexual relationships and felt unable to complain.

The Ministry of Defence was keen to state last week that there is no technical ban on consenting relationships — if both parties are single — but that the overwhelming emphasis is on the good of the team. If a relationship were to be formed within a unit, a spokesman said, the likelihood is that there would be administrative sanctions — moving one of the lovers on.

For those who have been in the forces, Henderson’s argument about recognising the “real world” is irrelevant. “Whatever outsiders say about extending civilian values and liberty of conduct to members of the armed forces — and that includes the question of positive discrimination as well — every issue must be considered in terms of the dangers and stresses which such a necessarily tightly knit community faces,” says Beevor.

Henderson retorts that all she wants to do is open a debate. Only then will the problems of recruitment and retention facing the forces be addressed. Otherwise she feels young people will simply not be happy to sign up and sign away their sex lives.

She remains unrepentant about the fact that she had a relationship with someone “between ranks” and is still on good terms with her former lover. “We keep in contact,” she says. “My God, it’s a long time ago but I think we are pretty sanguine about it and can look at ourselves in the mirror in the morning and say, ‘Yes, we did the right thing’.”