Martha Argerich’s personal loyalties are leading her to collaborate with ever more of her former husbands, partners, and friends. She frequently plays under the baton of ex-husband Charles Dutoit, and shares a four-hand keyboard with ex-partner Steven Kovacevich, as she did at this year’s Proms with her childhood friend Daniel Barenboim. Now she has used a four-hand recital to celebrate the 75th birthday of fellow-Argentinian Alberto Portugheis, who shared a teacher with her in childhood, and who at one point co-ran a London restaurant with her – he’s a master-chef, as well as being a pianist.

But Portugheis is not a major player: was it brave of him, or foolhardy, to share the stage with the greatest pianist in the world? The latter, one felt, as he struggled to match her in Mozart’s grandly orchestral two-piano 'Sonata in D K448': the poetry we intermittently got from her end only served to underline the lack of it from his. Rachmaninov’s 'Six Pieces Opus 11' emerged without any finesse as she tried to fit in with his erratic rhythms, but things looked up as Ravel’s 'Ma Mere l’Oye' gained increasingly confident momentum, while Brahms’s 'Opus 56' variations emerged muscular and triumphant, the magic Argerich touch saving the day. Encores: Piazzolla, and Le boeuf sur le toit.