When the British industrial designers Edward Barber and Jay Osgerby approach a project, they try to do one of two things. Either solve a “problem” with an existing design or capture the “essence” of that design in some new way. “People are very comfortable when they understand an archetype,” says Osgerby. “But in order to bring something new, you have to change it. So, our job is to update, and improve on, those archetypes.”

Take their Pacific Chair. With its castor wheels, business-like armrests and tall rectangular backrest it is indisputably a piece of office furniture. Except Barber and Osgerby have concealed all the sliding controls and levers now required (by law!) to adjust the seat, arms, backrest etc within the chair’s body, creating a “visually clean” version that responds to the individual weight of the sitter. It is no longer “a contraption”, as Barber has it, but the finest looking office chair you’ve ever seen.

Not sexy enough for you? Jony Ive disagrees. When Barber and Osgerby visited Apple HQ to give a talk to the in-house design team a couple of years ago, work on the new £3.5bn Cupertino campus for its 12,000 employees was nearing completion. “The one thing we cannot find,” Ive confided, “is a really nice-looking office chair.”

His guests fished out a phone and showed him their Pacific Chair, then in preproduction with the Swiss furniture company Vitra. “When’s it ready?” Ive responded.

This year, Barber and Osgerby celebrate 25 years in the business; not just that of updating office furniture, but large-scale architectural projects, interior design, sculpture, fabrics, tiles, desks, luggage, silverware, exhibitions, installations, coat hangers, showers, phones and shop facades. They have made lighting for Flos, chairs for Cappellini and tables for B&B Italia. Commissions have come from Louis Vuitton and Hermès, BMW and Sony, Coca-Cola and Levi’s. They designed the torch carried in the London 2012 Olympics and the £2 coin commemorating the 150th anniversary of the London Underground.

Barber and Osgerby have two more anniversaries this year: their 10-year-old Tip Ton chair, a stackable polypropylene design originally for schoolchildren that tilts with the sitter, thus straightening the pelvis and spine; and their first design, from 25 years ago, their Loop Table, comprised of two U-shaped sections of plywood joined seamlessly, a deceptively simple idea that from certain angles appears to float above the ground.

Their diverse output is unusual but then so are they: blue chip design studios tend to be Italian or German or Scandinavian. There aren’t many contemporary British duos whose work is in the permanent collections of museums around the world. In 2013 they were both awarded OBEs. It is all the more pleasing because, sat in their first-floor Shoreditch studio surrounded by boxes and bits of wood, they are amusingly unassuming.

“‘I’m a designer’ — it’s like the worst thing you can say,” says Osgerby, the shorter and more luxuriantly haired of the pair. “It’s embarrassing. We’re not wearing pink suits and standing on the table and being, like, ‘Yeah! Design is now.’”

“I don’t know if those people still exist,” sighs Barber, the taller and droller one. “They definitely did when we started out.”

That was when they met as architectural students at the Royal College of Art in South Kensington; their Loop Table born from experiments with “white card, cutting mats, Uhu glue and scalpels”. “We worked really, really, really hard,” says Osgerby. “Like, ridiculous hours. Just not on college work.”

The Loop Table became the first new design taken up by Isokon Plus, the furniture company that counts Walter Gropius and Marcel Breuer among past bosses, in more than 30 years. Within months, the Metropolitan Museum of Art in New York had bought it for its collection. “Then it went into the V&A,” says Osgerby. “We were very surprised. We thought, ‘This is alright!’”

The Tip Ton chair came via a commission from the Royal Society of Arts Academy in Tipton in the West Midlands. Dispatched to find out if school furniture was fit for purpose in the 21st century, Barber and Osgerby decided it very much wasn’t. “We spoke to all the staff and asked them what worked, and what didn’t,” says Osgerby. “Then you speak to the janitors and they go, ‘Come and have a look at this’. And you go out the back and there’s just piles and piles of broken chairs.”

“School furniture, the stuff you can buy, you get it through this sort of cartel,” says Barber. “The budget in this country is £11 a chair. What can you seriously make that’s going to last, for £11?”

Osgerby: “We wrote all these things down and said, ‘Why don’t we design a new chair?’ And they said, ‘Yeah, great! Who’s going to pay for it?’”

The designers went to Vitra, who initially thanked them but explained they didn’t do kids’ furniture. But they persevered and Tip Ton — light, robust, stackable, with a rocking motion said to boost oxygen supply in the sitter — is now a Vitra bestseller, in and out of classrooms.

They moved into their Shoreditch base in 2005 with a team of eight. They’ve since grown to 70-plus. With their salt and pepper beards and dad trainers, they fit right in; fashion-conscious creatives who’ve grown with their surroundings, which have been instructive. For instance, when they designed the neighbouring Ace Hotel in 2013, they noted how laptop café culture had transformed the area and planned accordingly.

“We designed this long table down the middle of the lobby, thinking the residents of the hotel will come down and work,” says Barber. “And it was completely taken over on day one by the local community.”

It led them to launch Soft Work in 2018: essentially a line of table-height sofas with power sockets, arm-mounted desks, partitions, wireless charging tables and super-padded upholstery, a modular system that can be clipped together in endless ways. It was intended to fit equally well into an art gallery as an airport or hotel lobby.

“The desk has had its day,” they announced at the time, shortly before the office followed it. “Things that we’ve foreseen in society have accelerated,” Barber says. “But what I think we’re particularly good at is seeing the fluidity of change and then taking it to manufacturers.”

They recently launched a future-proof version of their Tip Ton made from German post-consumer waste — yoghurt pots, to be exact. (“You can sometimes get a bit of yoghurt pot branding on the side,” Osgerby approves.)

Solving problems, capturing the essence of design: it is their happy place. For Barber and Osgerby’s most visible creation, the 2012 Summer Olympics torch, they conceived of a lantern-like curved aluminium tube, punch-cut with 8,000 holes to reference the number of torchbearers (8,000) and their joint running distance (8,000 miles). It needed to be tall enough to be visible but light enough to carry, hardy enough to maintain gas burning at 700°C but safe enough that children could run with it. Even the flame had to be a certain colour so it could be seen on TV. Most crucially, it needed to not go out.

“That was the main thing,” Barber says. “In the Olympic Museum in Lausanne, [Switzerland] we have, under our torch, ‘Best Performing Torch’.”

It got extinguished just twice, apparently. Once when someone put the wrong type of gas in it. And once on a canoe slalom in Hertfordshire, when it was taken white water rafting. “And that,” Osgerby says, “was never in the brief.”