But throughout its 50-plus years and its changes of personnel, some things have been constant.

The present members see themselves as inheritors of a tradition that began when four remarkable players came together to create inspired performances of the great classical and romantic chamber music repertoire.

The current incumbents will be in action for the Petworth Festival on Tuesday, July 20, at 7.30pm at St Mary's.

Rafael has been with the quartet since 2001, the result of a happy accident.

He'd succumbed to the classic injury of his trade – 'the sort of injury that people who paint or baseball pitchers also get, where the bone on your shoulder frays away the tendon'.

The Allegri needed someone; Rafael had met a surgeon at a party and been told about a possible operation; 'and I joined on the assumption that the operation would work. The operation took an hour and a half and was actually working the next day'.

Their Petworth programme includes major works by two giants of the string quartet canon and a brand-new work from the pen of lyrical English composer, Alec Roth.

They will play Beethoven: String Quartet in Bb major op18 no.6; Alec Roth: New Work (second performance); and Brahms: String Quartet No3 in Bb op67.

The Roth was the perfect model of commissioning, as Rafael recalls: "When you commission a work, there is always that moment when you first play it when you think 'Oh my god!'.

"But this piece works absolutely brilliantly. The first time we played a little bit of it, we were all smiling.

"It was a real joy. I recorded our first performance of it at Salisbury, and the people I have thrown CDs of it at are all delighted and have enjoyed it."

Sometimes the commissioning process can leave you performing a piece that you really don't believe in – absolutely not the case here, Rafael says.

"Ultimately, we are the advocates of a piece, though. We are not the judges!"

Tickets on 01798 344576.