BBC Proms: Piemontesi/ Navarra String Quartet, Cadogan Hall, London

With passport glitches, illness, and death wreaking havoc in concert schedules, we are seeing just how big the available pool of talent is. After all, many now-famous singers and musicians owe their careers to the sudden indisposition of a senior rival. Thus it was that the Navarra String Quartet were given an unexpected Proms debut, and the young Swiss pianist Francesco Piemontesi had just a day in which to find his modus vivendi with them, in one of the most demanding works in the chamber repertoire.

To Catherine Bott's amiable enquiry as to how this speed-dating worked, Piemontesi replied – slightly out of breath after stunning us with his Debussy – that "the human brain can achieve weeks of work in just two hours, if the pressure is intense enough". It clearly was: they launched into Schumann's Piano Quintet in E flat major with such assurance that they might have been collaborating for years.

This majestic work was written by Schumann as a miniature piano concerto which his wife, Clara, could perform in private houses. Piemontesi and the Navarras gave it the requisite declamatory spaciousness from the start. As with Schumann's piano concerto proper, the work involves constant dialogue between soloist and ensemble. With Piemontesi leading the way, they made a thrilling journey through an emotional landscape by turns sweet, spooky, throbbingly combustible and liberatingly joyous.

If that was a flawless performance, so was the Navarra Quartet's treatment of one of Haydn's early masterpieces, the G minor Quartet Opus 20. They have a warmly-rounded and very expressive sound, perfectly suited to Haydn. On this showing they are in the first rank of his music's exponents.

Piemontesi, one of the BBC's New Generation artists, is a brand-leader for Debussy. Using a completely different palette from the one revealed in the Schumann, he gave a series of preludes the most exquisitely translucent characterisation.

Representing victory snatched from the jaws of defeat, this concert, in the excellent Cadogan acoustic, was part of a highly promising Proms strand. It is just a shame that the Hall's front-of-house facilities, particularly for the old and disabled, are so unfriendly.