It is difficult not to notice the youthfulness of the face greeting us on stage (especially in comparison to the, shall we say, more weather-worn ones in the audience). But Benjamin Grosvenor has come a long way from the eleven-year-old that won the BBC Young Musician of the Year piano final in 2004. Now aged 21, Grosvenor is on a mission to prove that he is not only a prodigy, but also a mature and thought-provoking artist.

This might explain his unusual programme. Chopin and Rachmaninov, favourites for the piano virtuoso, are noticeably absent. Even if the first half is firmly rooted in the Austro-German tradition, instead of Bach, Beethoven and Mozart, we have Mendelssohn, Schubert and Schumann. The second half is even more adventurous, featuring lesser-known composers Federico Mompou and Nikolai Medtner.

Considering his quest to be taken seriously, it is surprising that Grosvenor will play in the less-than-ideal venue of the Drill Hall in Horsham, West Sussex. All the lights were left on so that the audience were as lit as the stage, producing a rather dry environment. Nevertheless, Grosvenor makes it difficult to concentrate on anything but his playing. After he had sunk carefully into the opening of Mendelssohn’s Andante e Rondo capriccioso, it was clear that for Grosvenor, every note matters. He produced a very concentrated sound that lured the songlike qualities out of the Andante. However, there was not enough contrast between the lyrical Andante and the playful Rondo. His generous pedalling during the Rondo theme meant that it lacked clarity, regrettably leading it to lose the fairy-like quality that is so important in Mendelssohn.

This can all be forgiven, however, for his intense concentration in Schubert’s Impromptu in G flat made for a thoughtful and poetic performance. Any concert pianist would be capable of a pleasant enough performance of this already beautiful piece, but Grosvenor paradoxically turned the act of performing into something astonishingly introverted – a feat that few could boast of. He coaxed from the piano a wistfully soft sound, never forced. The rustling of programmes and sniffling of noses were tellingly absent, as the audience was inescapably drawn to listen to every single note. Commanding a similar amount of attention was going to be a challenge in Schumann’s Humoreske, being a longer and relatively unstructured piece. While not as enrapturing as the impromptu, Grosvenor maintained interest by turning it into a journey through the work’s different characters: from the gentle, lullaby-like opening that transported us to a world of innocence, to the cheerful, the unnerving and the outright thunderous.

But Grosvenor still had a whole other soundworld to reveal in the second half. Paisajes (“Landscapes”) is a set of three short pieces by the 20th-century Spanish composer Federico Mompou. The influence of French Impressionism, Satie in particular, was quickly made evident in the first of the set, “La fuente y la campana” (“The Fountain and the Bell”), though he treated it far more seriously than any salon music. Grosvenor was content to let the music speak for itself, not letting his own personality interfere too much with the music’s own refinement.

The journey into unfamiliar repertoire continued with two Fairy Tales by the Russian composer Nikolai Medtner. Grosvenor played unabashedly in the loud sections of “The March of the Paladin”, but stumbled during the shifts into quieter moments. It was a confusing performance, with none of the direction of a march. Fortunately, he was more at home with Ravel. Grosvenor relished the luscious harmonies and swirling melodies in Valses nobles et sentimentales, as well as having no qualms in enjoying its moments of pure prettiness.

Still full of youthful flair, Grosvenor was at his best with the magnificent. There were glimmers of it in the Ravel, but it was only in the final piece, Liszt’s transcription of Gounod’s Valse de Faust, that he unleashed his virtuosity. His playing was shamelessly loud, the pounding bass producing a comically bombastic waltz. Though there was brief respite during a quieter middle section, it was astonishing that he could maintain the its sheer volume for as long as he does without losing any of his energy.

Although Grosvenor has not yet achieved perfection, the crucial word here is “yet”. By boldly tackling an unconventional programme, he is pushing himself in exciting directions. For the moment he may be still be at his best with the magnificent, but if the subtlety of his Schubert impromptu is anything to go by, Grosvenor is well on his way to becoming a serious interpreter of the concert staples.