This terribly respectable-looking Japanese lady was sitting on the Tube. Immaculately dressed in highly polished court shoes and neat, well-fitting dress, the sheaf of papers that she was reading rested on perfectly pushed-together knees. And yet everyone in the carriage, me included, kept looking at her legs. One man was showing his fillings. She was wearing fishnets. This was five years ago – when fishnets were really worn only for fancy dress or by ladies who knew the exact placement of all the CCTV cameras in the King’s Cross area of north London.

I, too, was enthralled, but for very different reasons. She was wearing cream fishnets and I knew these to be devilishly difficult to find. Back then, fishnets were only readily available in black and red. Feverish phone calls to the top hosiery stores of London led me to Fogal in New Bond Street (now closed). Ahhhh, should I wish to procure a pair, they had them in cream. I thought about it seriously, but courage failed me because, at that time, we were still in the grip of black opaques.

The Japanese have always been ahead of the sartorial game because, this year, fishnets are again fashionable. Although they have yet to be spotted in parliament, fishnets are worn by socialites, ladies of good repute, young girls, old girls.

For much of the Conservative era, boring black opaques were the only thing for legs to be seen in. They took off because it seemed like the easy choice for people too lazy to look for alternatives. (Am I talking about voting Conservative or wearing black opaques? Does it matter?) They lasted a long time, were easy to wear and de-sexed the wearer – all essential requirements for women at that time, who had to look as if they meant business, and that business was making it big in a man’s world. There was no room for feminine frippery, no time for laddered hose.

But hormones will out. Almost at the very moment that Labour took over, a nation’s collective sigh of relief showed on half its legs: hosiery changed overnight. New Labour was all about rediscovering your feminine side. It became acceptable to be emotional, to drop your armour of shoulder pads and show your legs again. Fashions changed. Sheers came back, as did funky, lacy tights. And now, fishnets.

As is fitting for such a saucy bit of hose, their exact provenance is murky. Stockings have been around for ever: as woven leg coverings since the 16th century – before then, legs were covered with fabric cut on the bias for stretch and would have been seamed.

But fishnets are not even mentioned in the hosiery bible Costume Accessories: socks and stockings (published by Batsford, although now out of print) by one of Britain’s leading experts on such matters, Jeremy Farrell, the keeper of the Museum of Costume and Textiles in Nottingham. And even he isn’t sure from whence they came: “Just the other day, I saw a mention in the Lace and Embroidery Review from September 1912 talking about ‘the new netted or fishscale hosiery’, so they were definitely about then.”

We deduce that fishnets probably evolved from stockings that had lace panels, then became all-over lacy and, from there, lazy lace: fishnets. “But where they got their slightly risque connotations from is anyone’s guess,” continues Farrell. “It was the same with black stockings. Initially, they were common, everyday wear and then . . . there was the opinion that, if you were attracting attention to your legs, you weren’t quite nice.”

“Fishnets came about with the leg shows at the beginning of the 20th century. I think,” says Ralph Salem, the managing director of Melas, the makers of Jonathan Aston hosiery and purveyors of fishnets in practically all colours. This makes sense: fishnets show off the leg while keeping it covered, and are incredibly warm because they trap air – which must have been handy in the unheated dressing rooms of the Moulin Rouge. Also, fishnets are hard-wearing – they are warp-knitted, as opposed to weft-knitted like other types of tights. In the Fifties, they were often worn by starlets; in the late Seventies and early Eighties, they were ripped and worn by punks (often over a pair of red tights). The absolute must-have fishnet at the moment is the really wide-net version – although the micronet, whose holey bits are very small, might be better for the hesitant; and for the purist, there is the classic fishnet.

Anyone who remembers them from the last time around may be fearful of the Achilles’ heel excess. Fishnets were famous for not following the contour of the heel, and bagging unattractively. Fear no more: the addition of Lycra provides a snug fit. Although black is still a very popular colour, fuchsia, creams and burgundy are also frontrunners. Jonathan Aston also does a roaring trade in “red fishnets in Portsmouth”.

Why have they become so fashionable again? “We are coming out of a very dull time,” says Salem. “For years, it was black opaques. Now we’re back to showing legs again. And fishnets are accepted as being fashionable, without being over the top.” However, fishnets have yet to take off in the north of England. “But most fashions start in the south and then move up,” advises Salem.

So it’s fishnets for everyone now. And only time will tell if we’ll look back in embarrassment.