Star rating: **** The threat of disruption loomed before the concert, in the form of a placard outside the Queen's Hall accusing the Jerusalem Quartet of being partners in crime. Though the police were doing bag checks at the front and rear entrances, Palestinian supporters managed to infiltrate the audience and bring the opening Haydn string quartet to a halt. A man was dragged out shouting that the players were Israeli army musicians. The players left the platform.

In the course of further starts and stops - one more in Haydn's Op 76, No 5, two in Smetana's Quartet No 1, a work of strong Czech nationalist feeling - and of further protests from different parts of the hall, one of the players made an eloquent anti-political speech from the platform and the audience burst out clapping. Jonathan Mills, the festival director, stepped forward to express his belief that there were more movements still to be performed than there were protesters left in the audience. In thus calling their bluff, he established calm. The performance of Brahms's Quartet No 2, which completed the programme, was interrupted only by the first violinist breaking a string, and causing the briefest, jolliest of stoppages in the concert.

But what of the performances? Whatever effect the protesters had on the players, it sent what could only be called an increased charge of emotion through their playing. Each time they resumed after a stoppage, their tone gained fresh resolve. After the fourth halt, in the slow movement of the Smetana, the protests began to seem counter-productive. This was playing of high expressiveness, not least from the young cellist, whose instrument, originally Jacqueline Du Pre's, had been loaned to him by Daniel Barenboim. Though the presence of Barenboim himself in the audience would have been welcome, the music prevailed potently on its own.

Supported by Lean Scully EIF Fund.