The cover of Khatia Buniatishvili’s new CD of Schubert features the Georgian pianist in Pre-Raphaelite pose as John Millais’ Ophelia, draped in white, clutching a sprig of hogweed, immersed in the water. I’m not sure quite what marketing message this is meant to convey about her approach to Schubert’s final piano sonata – the great B flat major, D960 – but in her Barbican recital last night, it wasn’t Ophelia who was drowning. Alas, it was poor Franz who was engulfed, tangled in weeds, submerged beneath a perverse interpretation.

The first two movements were ponderous to the point of stagnation. The Molto moderato set off at a funereal pace, its deliberate tread halting at the hollow bass trill. This was soporific Schubert – aural Temazepam – with elastic rubato and pregnant with pauses, none longer than the chasm of silence before the exposition repeat. Buniatishvili kept a lid on the dynamics – much of this movement is marked piano or pianissimo – but the ruminative tempo was ruinous to any sense of flow or direction. She somehow dragged the Andante sostenuto second movement out to a lethargic 15 minutes (most pianists take around nine), at which tempo Schubert’s tragic introspection turns into glum navel-gazing.

And then Buniatishvili snapped out of her torpor, impatiently bursting into the Scherzo before the inter-movement applause had died down. Marked Allegro vivace con delicatezza, there wasn’t much delicacy in a hectoring sprint, smudged articulation and an insistent left hand uglifying the music. The opening G of the finale fired off like a starter’s pistol, the movement grossly caricatured. This was a schizophrenic, eccentric reading, Schubert played as if it was Liszt.

And it was Schubert through the prism of Liszt with which Buniatishvili opened the second half of her recital. Liszt is very much at the core of her repertoire and the three Lieder transcribed by the Hungarian virtuoso suited her far better, even if Gretchen’s spinning wheel jolted a little unevenly early on. She spun a fine cantabile line in Ständchen, phrasing naturally, but it was the fingers-of-steel, wrists-of-iron rendition of the ghoulish Erlkönig which signalled Buniatishvili reaching top form.

Mazeppa, one of Liszt’s most fiendish Transcendental Études, was given the full snorting stallion treatment, appropriate for its subject matter. It depicts Mazeppa tied naked to a horse (he had been discovered with a courtier’s wife), and the horse is whipped so severely that it gallops for three days, deep into Ukraine, where he is rescued by Cossacks who make him their leader. Buniatishvili rampaged through the terrifying runs in thirds, hammering the octaves of the main theme. It’s a wonder the keyboard didn’t spontaneously combust.

The same astonishing attack was evident in Liszt’s Hungarian Rhapsody no. 6 in D flat major, but with use of rubato and teasing hesitations as the start of the friska section, where repeated notes mimic the cimbalom so evocatively, tossed off with no more than a wild flick of her hair. And it was the friska from the Second Hungarian Rhapsody, as outrageously vamped up by Vladimir Horowitz and the Georgian herself, which provided the thrills in her first encore... including elbow glissandos! Peak Liszt. Peak Buniatishvili.