Counted among the community of great pianists on the world stage today, Angela Hewitt is also one who stands apart. She is perceived as occupying the doughty position of a persona re-invented, emerging from her previous incarnation as Bach doyen to a now fully-fledged proponent of the wider panoply of piano repertoire – a transition she has managed to spectacular effect, astonishing those for whom, until recently, her name was linked solely to the Baroque master.

For my money, Hewitt in full-blooded Romantic vein is vastly preferable. Her Bach-playing, thought by many to have served its time, continues to attract controversy: lauded on the one hand for its armoury of tonal nuance and poise, and dismissed on the other as lightweight and innocuous. Lacking the visceral quality – some may say clout – of the idiosyncratic Glenn Gould and Rosalyn Tureck before her, Hewitt nonetheless shares that fierce musical intellect common to all Bach pianists – a searching, forensic musicianship heightened and honed through the interpretation of the most exposing and subjective of all composers on the modern piano. How all this infects the playing of later repertoire is one of those rarefied questions I pondered only briefly in tonight's non-Bach programme. For, whilst the digital precision, the clarity of articulation and keen grip on structure were evident, the pervading sense was one of a romanticist breaking out, with the occasional excessive whimsy, from that contained, more cerebral world.

Three of Schubert's Moments Musicaux, Beethoven's “Tempest” Sonata and the Fantasia in C major by Haydn Hob XVII:4 made superb companion pieces in the first half of the programme, with the Iberian second half (if we call Scarlatti an honorary Spaniard) comprising four Scarlatti Sonatas, three movements from Albéniz's Suite Española and Fantasia Baetica by de Falla.

Her Schubert was imbued with a poetic sense of narrative, the second of the set particularly notable for Hewitt's melancholically singing right hand and in the third, despite some loss of top line clarity in the chordal right hand, the Slavonic 'air russe' temperament was irresistibly well captured. Hewitt amply demonstrated her gift for narrative in a compelling and highly-coloured account of the Beethoven Sonata Op.31, no. 2, distinguished by a beautifully expansive Adagio middle movement. But the opening movement was marred by her tendency to emphasise the gesture at the expense of the pulse. A more rigid hold on tempo would have facilitated greater clarity and provided steadier ground: the rhythmic shape of the low growling left hand scalic passages was never quite defined. The Haydn too, though clearly intended to have maximum dash and verve, felt a touch precipitous.

But it was in the Scarlatti where liberties took too great a precedence and where the question of any affliation with Baroque sensibilities seemed to evaporate. Indeed these harpsichord pieces had rubato-infused Romanticism fairly thrust upon them, with K24 in A major suffering in particular from an apparent need to overstate the simplicity of the gesture and maximise every opportunity for pianistic nuance at the expense of pulse.  It seemed somehow counter-intuitive that the essential Scarlattian rhythmic 'swing' – that robust Spanishness – could get so lost in translation: Ms Hewitt played Scarlatti as if it were Albéniz. Indeed, I hardly noticed the 200 year leap to the Suite Española: here, in these masterful fusions of traditional Spanish dance forms and virtuoso piano techniques – where sweeping gesture and sensuality are inherent in the musical fabric – Hewitt proved the consummate executor. Eschewing gratuitous bravura and self-conscious rubato, she was at the service of the composer and truly worthy of his wish: "I want the Arabic Granada, that which is art, which is all that seems to me beauty and emotion."

De Falla's Fantasia Baetica, the towering masterwork of 1919 which famously floored Rubinstein, requires power-house technical skills and runs at almost 13 minutes. Redolent of the Iberian landscape, de Falla the great orchestrator can be heard at every turn, as can the melodies and rhythms of ancient Andalusia with its traditions and spirit of “tzigane”. Hewitt excelled, holding the audience in a powerful grip with a performance of great elan: her palette of tonal colour and accent and her chord-spreading – like massed guitars – promise to abide long in the memory.

And as if to assuage my earlier misgivings, the performer's favoured encore of Scarlatti K380 in E major was blessedly measured, and with Baroque cool.