Obviously I didn’t think they were all virgins, just because they worked for a company with the V-word in the title. That would be ridiculous, wouldn’t it? But then I never imagined it was compulsory for female cabin crew at Virgin Atlantic to wear makeup and tight skirts when they were serving meals, dealing with sick children or – in the worst possible scenario – guiding terrified passengers through emergency exits on to inflatable slides.

On Monday, in a sudden lurch into the 21st century, the company relaxed its strict dress rules, announcing that female cabin crew would no longer be obliged to work wearing full slap. It also decreed that trousers would be available as a standard item in the Virgin Atlantic uniform, instead of female flight attendants having to make a special request. I mean, how modern is that?

Women who choose to wear makeup while they are working on board will still be expected to abide by the “palette” set out in company guidelines, however. Red and white, like the logo? Whatever progressive message the company was intending to send out was immediately contradicted by a boastful tweet showing Virgin Atlantic’s newest cabin crew apprentices: 18 women, identically dressed in tight, above-the-knee skirts and red lipstick – and just three men.

Until now, I had no idea that such discriminatory dress codes still existed, let alone that they complied with the law. I had a vague memory of a woman being sent home from a new job two or three years ago for refusing to wear high heels, but assumed that such sexist requirements had long since been outlawed. How wrong can you be?

There was indeed an outcry after Nicola Thorp was sent home in 2016 from her job as a temporary receptionist at PwC’s outsourced reception firm Portico because she was wearing flat shoes. There was even a petition with more than 150,000 signatures, calling for a ban on the practice, which I’m pretty sure I signed. But Theresa May’s government, with its instinctive dislike of regulating just about anything, argued that existing legislation was “adequate” to prevent gender-based discrimination.

Hence the perfectly legal nonsense of women who work for airlines being told they have to wear eyeshadow and lipstick in shades approved by the company as a condition of the job, unless and until management graciously consents to emerge – with lingering backward glances, no doubt – from the 1950s.

Three years ago, cabin staff at British Airways successfully challenged a requirement that new female recruits had to wear skirts unless they were exempt on – wait for it – medical or religious grounds. Budget airlines such as easyJet are more relaxed about female employees wearing trousers, but Ryanair only stopped publishing a calendar featuring female cabin crew in bikinis in 2015.

All of this is risible, especially in an industry that relies on some of the world’s most advanced engineering technology. But women who work on board complain that having to wear a stereotypically feminine uniform sends subliminal messages to passengers, encouraging them to treat female cabin staff as little more than handmaidens.

It also appears to send a negative message to their employers when it comes to setting salary levels. Virgin Atlantic has a significant gender pay gap, according to figures published last year. Its median hourly rate for women is 30% below that of men, something that means – as the government’s gender pay gap report painfully spells out – that women earn 70p for every £1 that men earn. (The gender pay gap at British Airways, by contrast, was 10% in 2017.)

Clearly, this habit of sex discrimination is very hard to break. It starts with dress codes and ends with salaries (or doesn’t – let’s see what this year’s report on the Virgin Atlantic pay gap has to say). One minute you’re telling women what colour lipstick to wear, the next you’re paying them less as well. How on earth does that happen?

Perhaps, and I’m just making a wild guess here, viewing male and female staff through a different lens isn’t a minor matter after all. Female cabin crew have proper jobs, which might one day include having to perform CPR on a desperately ill passenger, and they don’t need to do it in tight skirts and perfectly applied lippy.

But then maybe I’m expecting too much from a business empire whose origins can be traced back to the 1970s, when it was still considered daring to name a mail-order record business after a stock figure from male fantasy.

• Joan Smith is a columnist, novelist and human rights activist