Even in times when you’re more likely to be eating dinner on the sofa than at the table, it’s worth remembering the oft-repeated aphorism, “a gentleman uses a butter knife even when dining alone.” This isn’t about Downton Abbey pretensions, or Brideshead Revisited fantasies, it’s about living elegantly, and by extension dressing elegantly, wherever you are, even if (and especially if) you might not feel like it.

That said, we’re the first to recognise that comfort is a priority, and the more formal a working wardrobe a man is used to, the more important it will be for him to take it off when work is over. The logic of this, however, isn’t to throw on an old pair of NBA replica shorts and a greying wife-beater, but instead to seek out superior loungewear. At its best this takes the form of a pair of pyjamas and a dressing gown, a combination as comfortable as a sweat suit, but as elegant as a tailored one.

If you’re still unconvinced of the need to dress up at home, it’s relevant to mention that, aside from delivery drivers and neighbours, the people who see you in your loungewear are the people whose opinions really count: loved ones, partners and children. Of course, it’s true that no man is a hero to his valet (as Mr Michel de Montaigne observed in the 16th century), but that’s a reason to try harder in the company of your nearest and dearest, rather than relax into the sartorial depravity of three-day sweatpants.

Plus, pyjamas make a statement. They speak of an age when men had time to read a newspaper while they ate breakfast and enjoy a quiet glass of whisky before bed. They also tell a tale of much draughtier bedrooms than we’re used to, and hark back to the (now unthinkable) days when gentlemen didn’t work; the era of Sir PG Wodehouse’s fictional character Bertie Wooster, who rarely rose before 9.00am, and is said, in 1934’s Thank You, Jeeves, to wear heliotrope-coloured pyjamas.

For good or bad, those days have gone. However, they still have a lot to teach us about style, elegance and doing things well, even if it’s sometimes hard to achieve these things while having to simultaneously earn a living.

Perhaps it’s telling that Sir PG was unlucky in love because, whatever men did in the 1930s, these days there is one domestic situation for which pyjamas are ill-suited. If, after a date, a man is entertaining in his bedroom, especially if it’s the first time he’s entertained this particular date, then classic white cotton boxer shorts are probably the best option. The truth is that pyjamas’ easy cut, and the fact that they cover the entire body, means that they’re more sophisticated than seductive.

Assuming the white boxers are well received, and more dates follow, then after the initial frenzy of love has relaxed into something more dependable, a man may revert to wearing pyjamas. Complete the outfit with a proper dressing gown (keep the towelling bathrobe for the bathroom), and a pair of velvet slippers. And if you do get to get up in time to enjoy breakfast in your splendid new nightwear, then do remember to use a butter knife when you prepare your toast or croissant.

Is that a booty call, Mr Grant? Probably not, given that the actor has made the nerdy move of buttoning his pyjama top right up to the collar. But what this look lacks in animal appeal it makes up for with its abundance of smooth sophistication. Accessorise with a good book, an early night and neatly parted hair. And don’t forget to floss.

This charming shot of the French singer, who was replying to fan mail at a stage in his career when his bedroom still had posters of his idols on the wall, sends two contrasting signals. Mr Johnny Hallyday is in white pyjamas, but with the buttons undone; the message seems to be, “I’m only pretending to be innocent”.

The life of the writer, it’s tempting to conclude from this shot, consists of days spent lounging decorously at home. While this conclusion glosses over the anxiety, coffee and online meetings involved, the photograph does accurately convey the fact that when it comes to sitting about reading, pyjamas are the garments that best balance elegance with comfort.

It’s hard to imagine a calmer way to start the day than by drinking tea, wearing a dressing gown, with a dachshund on your lap. Here Mr Marlon Brando, who’s in Los Angeles, shows that a man can still look eminently smart in his bedclothes. The tea might be at a drinkable temperature, but at least the pyjama piping is hot.

This American actor’s eye-catching but relaxed outfit shows why the 1930s remain a high point in the history of male elegance. The polka-dot dressing gown grabs our attention, but its verve is balanced by Mr Thomas Beck’s plain pyjamas. However, it’s the polished leather slippers that really distinguish this look.

Sharing a pair of pyjamas with a woman works extremely well; she’ll look good wearing just the top, and you’ll look good wearing only the trousers. In this shot, Mr Marcello Mastroianni pretends to be asleep while Ms Brigitte Bardot stretches, proving that simple solid colours work as well on French starlets as they do on the rest of us.

The people featured in this story are not associated with and do not endorse MR PORTER or the products shown