What is a piano trio? The art form goes back to Haydn, but it’s always been seen as a side-show to the quartet tradition which Haydn and Beethoven took to unparalleled heights of inspiration.

A violin, a cello, and a piano sounds simple enough, but the three works which the Gould Piano Trio are presenting at St Jude’s Church in Hampstead Garden Suburb will show what musical wonders can be conjured up by this unassuming combination.

It’s perhaps inevitable that this shadowy art form should not have boasted many exponents. When the Gould Piano Trio was formed in 1987, even music buffs would have been hard pressed to name many others beyond the Beaux Arts Trio, who put the form on the map in 1955. They are now no longer rarities, but it’s a measure of the Goulds’ achievement that their playing should now be compared to the Beaux Arts themselves.

Their composition has changed over the years, with violinist Lucy Gould remaining the constant. She and two friends didn’t set out to be a piano trio, "but we were students at the Royal Academy, and chamber music was what we did all day". They got tuition from the surviving members of the Amadeus Quartet – Jewish chamber-music royalty who had all met in an internment camp on the Isle of Man – and did well in competitions – so the trio just emerged.

The latest recruit is the distinguished cellist Richard Lester, but his pathway in was a family thing. After the break-up of the Florestan Trio he had spent six years without a trio, wanted to join another, and gradually something clicked: "Lucy was my sister in law - I’m married to her sister who is also a cellist - so I’d been on the fringe of her trio for a long time."

"We head-hunted him," jokes Lucy. "We decided that he was the only person capable of doing the job."

The group is close-knit, yet they all have demanding orchestral and teaching jobs. Lester teaches at the Royal College of Music and the Guildhall, Gould teaches at the Royal Welsh College of Music and Drama, and pianist Benjamin Frith teaches at the Royal Northern College of Music in Manchester. Meanwhile Lester and Gould are both principals in the touring Chamber Orchestra of Europe.

How much has Brexit affected them? Lester lets fly: "It’s an extreme annoyance. All it does is create endless bureaucratic problems, and absolutely zero benefits. Things aren’t quite as bad as they were at the beginning, when there was absolute panic among musicians over having to get visas to go anywhere. At least that has eased a bit, though some countries – like Greece – still insist on them. Spain thought of imposing them, but then backed off. It’s just utterly stupid and pointless."

Gould points out that the biggest problems are for musicians who have to tour a lot, notably opera singers who fall foul of the 90-day rule. This decrees that Britons can only stay in a European country for ninety out of any given 180 days. "And opera singers often have to commit to long rehearsal periods, with theatrical runs spread over many weeks."

She also points to a different EU problem: "For example, I borrowed five bows from a German musician, and I literally don’t know how to get them back. They are old bows with ivory parts, and could easily get confiscated. But otherwise we’ve not been massively affected as a trio. But our orchestra has had to establish a new base in Europe, simply to go on functioning."

How have things changed for student musicians, since the trio were starting their careers?

Lester: "It’s much harder now than it was for us. The competition is hugely greater. I’ve just been involved with a cello competition in Brussels, and I couldn’t believe how high the standard of playing now is. Everybody could play pretty much perfectly. Whether they were really good or not is another question, but the technical level is terrifying."

He adds that the musical world is getting smaller, with many traditional sources of work – like local-authority funded music societies - closing down.

"And as there isn’t the work, they do all they can to remain perpetual students, living on grants. They need to be warned at the outset that it’s really tough out there."

The other big thing which Lester noticed in that competition was the almost total absence of British players. "Lots of South Koreans and Chinese and Europeans and Americans. It’s like the sports world – we are evolving, and people just keep getting better and better, and world records keep getting broken. But all this doesn’t mean that these players are becoming musically more interesting."

Which leads Gould to make a political point which can’t be stressed too much: "Fewer and fewer children are learning to play an instrument at school. Very few young instrumentalists come through the normal state school system – the ones who come out on top have been trained in private schools and specialist academies."

Tell that to the Government? Don’t waste your breath.

The Gould Piano Trio play St Jude's Church on June 30 at 7.30pm performing Beethoven Variations in G Minor Op 121 Kakadu, Saint-Saens Piano Trio No 2 in E Minor, and Faure Piano Trio in D Minor. The Proms at St Jude's Festival 2022 runs June 25 until July 3. Visit www.promsatstjudes.org.uk/2022-evening-concerts