While Debussy was the headliner in this opening concert of the London Symphony Orchestra’s sequence in his name (three concerts are not quite a season), François-Xavier Roth included only one of his works in a programme that came weighted with major pieces by Wagner, Lalo and Massenet. The reasoning was simple: young Claude’s early and newly unearthed Première Suite d’orchestre, hitherto unheard in the UK, was presented in the context of music that may have inspired him.

As an early exercise in composing for a large orchestra the 1884 Suite is certainly ambitious. It is unambiguously French but not unmistakably the work of Debussy except, oddly, in the third of its four movements. That's Rêve: a proto-impressionistic swirl of shimmering strings and harps that pass melodic fragments to the woodwind and on again to the full orchestra. Why ‘oddly’? Because Rêve is the only section whose orchestration remains lost, and its reclamation from a piano score is the expert work of Philippe Manoury. As for the other three movements, they give barely a hint of the road yet untravelled. Fête is a lushly generic carnival piece, Ballet much the same but heavier on the orientalism, Cortège et Bacchanale a brass-led procession with a catchy hook to its recurring fanfare motif. It’s a fascinating if unrevealing discovery, then, albeit one that Roth, the most respectful and probing of conductors, treated as a masterpiece.

An unequivocal masterpiece had opened the concert. Wagner’s Tannhäuser Overture is not only a succinct summation of the opera’s three hours to come, it’s a series of powerful melodic avenues that meet and intersect with thrilling panache. Roth’s account of it was remarkable: vibrantly expressive yet never febrile, the French maestro used his fingers like ten batons in a performance that seemed to deconstruct the orchestral texture then reassemble it so that every layer of sound existed within its own halo. Roth has conducted the full opera at Oper Köln so he has it safely in his pouch, and the LSO responded like Wagnerian gods.

Roth’s fellow-countryman, 23-year-old Edgar Moreau, has plundered their shared patrimony and unearthed Lalo’s showy Cello Concerto, a work that threatened to come into favour when Paul Tortelier championed it in the 1970s but has since been a rare visitor to British concert halls. The dapper young cellist played it proficiently but did not succumb to its rough-and-ready charms: his platform demeanour, courteous and correct, affected his playing of a score that freewheels joyously and without undue sophistication. Virtuosic moments were undercooked; indeed, in a couple of places the soloist’s rapid runs were too muddied for all the notes to cut through. This is not great music – the cheap sforzando chords that pepper the orchestration in Lalo’s opening movement quickly outstay their welcome – so the concerto’s execution needs greater showmanship than Moreau achieved if it’s to make its mark.

The Suite from Massenet’s Le Cid, a ballet that postdates Debussy’s Première Suite by a year, comprises seven movements of an irresistible Spanish flavour, all classically titled, that burst forth with greater pizzazz and less glucose syrup than his operas tend to do. Roth and the LSO let fly in music that seems to anticipate the Poulenc of Les Biches more than anything Debussy went on to compose. The Aragonaise would not be out of place at a New Year’s Day concert, while Massenet's Madrilène was a giddy round of galloping horses and false endings. I’m not sure anyone could dance to the closing Navarraise at Roth’s chosen speed, but a breakneck LSO played the heck out of it.