‘If you don’t mind my asking, how did you get invited to a state banquet in Luxembourg?’

It’s not in every shop that you’ll overhear an assistant asking a customer that question, but Oliver Brown is apparently one.

To enter the cosy world of the Sloane Street men’s outfitters – asymmetrical walls, rickety wooden floors, stag’s head above the stairs – is to enter a club-like environment untroubled by the fickle fads of fashion or the merry-go-round of seasonal trends.

The shelves are stocked with long socks and tweed caps. The tables are piled with corduroy trousers and merino V-necks. Boxer shorts come in all manner of colours. The staff discreetly glide about with tape measures around their necks. A picture of Prince Harry, photographed outside the shop in his Household Cavalry gear, hangs near the pyjamas. A bell rings above the door as you enter.

‘We’ll do summer suits in the summer, and tweed suits in the winter,’ says affable owner Kristian Robson as he shows me round. ‘Our eveningwear is across here. Smoking jackets, shooting gear… we do all that. We cover all situations for the gentleman.’

Now in its 23rd year, the formalwear and country-attire brand has never been busier. The post-Covid bounce has more than offset a potentially ruinous lockdown during Royal Ascot. Meanwhile, rumours of the death of the suit have been greatly exaggerated.

‘We ran out of suits very quickly [post-lockdown],’ says Robson. ‘People had all this money they hadn’t spent. A lot of them bought suits for their kids going back to school that August, so we became very busy very quickly.’

A second shop opened on London’s Jermyn Street in September and there’s talk of a third – potentially later this year. Online is going great guns, and wholesale is up and running. International sales are also booming both in the States and across Europe. English tradition is what these overseas customers want, and Robson is happy to provide it. He says he’s had more Americans through the door recently than at any time in the past 15 years. The weaker pound? ‘That – and our reputation,’ he says.

Robson acquired Oliver Brown in 1999 after his then-girlfriend’s father called him up and told him to buy it – the shop had gone into liquidation, and he couldn’t get hold of his corduroy trousers.

‘I called the number on the door and offered them something very silly’ – he means small – and he was off.

Today’s well-known customers include Eddie Redmayne and Damian Lewis, alongside royals he can’t talk about, peers of the realm he can’t talk about and MPs he’s got to talk about, because the most famous one was all over the press wearing ‘a rented £495 Oliver Brown suit to COP26’. Namely, Boris Johnson.

Was that good publicity or bad publicity? He looked as if he’d slept in it. ‘I know, I know, I know,’ Robson smiles. ‘It was a bit of both. I’ve met him and I thought he was hilarious.

‘We’ve had Gove in, the Minister for Health, the Chancellor… Loads of them, actually.’

Still, one member of the cabinet eludes him. ‘I’d love to make Rishi suits,’ he says. ‘I don’t know where he goes, but I’ll get to him.’

He thinks about this.

‘Boris has been back in. So the next time he comes in, I’ll ask him to introduce me…’

That would be a good get.

Bet Rishi gets invited to a few state banquets in Luxembourg.

Visit Oliver Brown at 75 Lower Sloane Street, London SW1W 8DA and 75A Jermyn Street, London SW1Y 6NP; oliverbrown.org.uk