Kanneh-Mason, Fantasia Orchestra, Fetherstonhaugh, St Gabriel's Pimlico

Sheku Kanneh-Mason isn't just BBC Young Musician 2016 - he's the year's top player in my books, a master at any level. Despite a contract with Decca, starting with the Shostakovich First Cello Concerto he played in the competition finale, he looks likely to remain loyal to family and friends, including the Fantasia Orchestra, founded this year, in which he's already played as part of the cello section.

You have to pinch yourself to realise the ages delivering this quality. Kanneh-Mason is 17, as was Mendelssohn when he composed the work of total genius which launched last night's concert; conductor Tom Fetherstonhaugh, currently Junior Organ Scholar at Merton College, Oxford, is 18; many of the players in the Fantasia are younger still, coming as they do from junior as well as senior conservatoire orchestras (another Kanneh-Mason, brother Braimah with whom Sheku spars so charmingly in the fabulous BBC documentary, is one of the first violins). Kanneh-Mason was, of course, in the limelight, and the original reason for heading out to a high church in Pimlico, but this concert delivered so much more.

Those strings, for a start: no orchestra sets out into the woods of Mendelssohn's A Midsummer Night's Dream Overture without some discipline and ability to master its flitting fairy music. These violins absolutely could, precise from the start, and there were even artistically portamento-d "hee-haw"s in the rude mechanicals' bergomask dance. The strings' buoyancy in Haydn's C major Cello Concerto was almost as much of a delight as Kanneh-Mason's playing (the cellist pictured above with the orchestra in rehearsal), and he acknowledged it by stepping back into what amounted to an obbligato role in the finale, keeping it light rather than showy.

The technical difficulty of the work can be disproportionate to its effect, but Kanneh-Mason's intonation was near-perfect, his dynamic shading kept us focused and he even managed to make the minor-key mood at the heart of the Adagio sound profound. So much of his artistry is akin to the lessons of bel canto; there were parallels with Lucy Crowe's feather-light coloratura the previous evening in the virtuoso runs, and he even emulated the singer's messa di voce, swelling a phrase to a peak and gracefully retreating, in some of the most fiendish writing.

This is an instinctive artist who seems fully-fledged already, like Bryn Terfel or Angela Gheorghiu at the start of their careers - but Kanneh-Mason is even younger. And he now has on permanent loan from Florian Leonhard Fine Violins the 1610 Amati which contributed to his success in the BBC final to gild his subtleties. Fetherstonhaugh, in a personable, confident speech, had apologised for the lack of Christmas theming in the programme, managing to justify the Mendelssohn by mentioning its use in seasonal ballets by Ashton and Balanchine. No need: we can all dream of summer nights in the dead of winter, and then up popped Holst's tune for "In the Bleak Midwinter" as theme for a nimble set of variations in Kanneh-Mason's encore, his own work (like the impressive first-movement cadenza in the Haydn). Besides, there was also the panache of the Waltz of the Flowers from Tchaikovsky's The Nutcracker as the grand, unprogrammed finale (pictured below: Fetherstonhaugh and the orchestra at the end of the concert).

Even so, you don't get grander or more Tchaikovskyan than the great perorations of Sibelius's Second Symphony. Listening to the big tune or the rolling tide of lower strings in its dark counterpart, it was hard to believe you weren't listening to the best. Take the violins in the first statement of Sibelius's big Tchaikovsky melody, or the brilliant, silver trumpet of Alex Ridout, heroic throughout, capping the brass response (earlier, there was terrific presence from Johnny Mayers' tuba in Mendelssohn's forest, and the oboes had a very Sibelian bite in the scherzo).

The asymmetries of the radical opening Allegretto seemed to pose no difficulties for Fetherstonhaugh. Of course it's always fascinating to see where the pressure-points of this amazing work lie for a junior ensemble: clearly at the heart of the stalking slow movement and in the big build to the finale. But other difficulties which I've heard conductors bungle on disc and in concert, like the mad rushing just before the Tempo Andante comes to rest and the brief surfacings of the first movement's oscillating main idea as it flashes into being, were beautifully handled.

Fetherstonhaugh's style is low-key - no flapping around - and in firm control; in time he'll learn to loosen up in the shoulders and paradoxically acquire more of the right tension, too, but I've not been called upon to judge an 18-year-old conductor before. Clearly he's a splendid trainer; that violin section is already a thing of wonder. And yes, we got all the right goosebumps in the Sibelius finale and the Tchaikovsky waltz - not always guaranteed even by the best.

• David Nice's blog on Sheku Kanneh-Mason in the BBC Young Musician final
• Read more classical reviews on theartsdesk