Mencyclopaedia: Derek Rose - Telegraph A pukka pyjama maker that's pushing the envelope in underwear. Overblown rhetoric about underpants is everywhere; one title recently dedicated several pages to "the death of the boxer short" and David Beckham's "bodywear" collection for the Swedish retailer H&M was launched with more pomp than a Hollywood premiere. This is because smalls are big business: in Britain men spend around £800 million a year on (their own) underwear, according to Mintel. And this is why Sacha Rose, a third-generation pyjama baron, is overseeing a radical reform in the 97-year-old family firm of which he is managing director. Mencyclopaedia: Fred Perry Derek Rose, named after Sacha's father but founded by his grandfather, has for decades been the best-known British producer of top-notch pyjamas. First imported from Asia when the British Empire was at its height, these loose, drawstring trouser and shirt combos, once adapted, proved as comfortable to sleep in at home as they had been to drink sundowners in while on commission. Modest yet comfortable, the pyjama-suit muscled into nightshirt territory, then fast-tracked itself into the canon of masculine attire. John Lennon wore them, Inspector Clouseau wore them, David Niven wore them, everyone wore them. Derek Rose The sun started to set on the pyjamas during the 1990s, reports Rose. Sales have been in slow decline ever since. This reflects a broader change in taste: for as the man in the street now dresses less formally than ever, the same has followed between the sheets. Unconsciousness no longer demands a collar. So while pyjamas might not yet be entirely passé (they still account for around two thirds of Derek Rose's sales), several years ago its managing director began to diversify. "Loungewear" is to pyjamas what the computer is to the typewriter. "Once upon a time a man might have put on his smoking jacket at the end of the day," says Rose, "and then it was jeans and a T-shirt. Now it's become even more relaxed. The stand-out "loungewear" items by Derek Rose are its Basel shorts (£68) and T-shirt (£68), which are made from an Austrian beechwood fibre, MicroModal, blended with Lycra, and which feel disconcertingly as if they aren't there at all. Mencyclopaedia: Canali Since 2010 Derek Rose has been planning its next development - an assault on that lucrative men's underwear market. Backed by a technical team with 122 years' collective expertise, Mr Rose has analysed hundreds of styles from across the world. "My drawers are overflowing." His conclusion? The market is enormous and there are a lot of people making terrible products - if you put a strong name on them, though, they seem to sell. One of the best-selling products at the top end is a white jersey boxer short, but it has a button you have to undo to open the fly. We asked anyone and everyone - and nobody was using that button. Rose's solution, boxer shorts (£38) with a newly patented magnetic fly-fastener ("there are no health issues; it won't go off in airport security") are just one innovation in a collection of mostly plain Pima cotton boxers and briefs (pictured left) that lack a famous name emblazoned on the waistband, but have been made with great care. You can still buy marvellous pyjamas, slippers, and nightgowns at Derek Rose. Its future, though, is in lounge and underwear - and those reports of the death of the boxer short seem premature.