It's time to reassess Gilbert and Sullivan

They are musical geniuses, says Jessica Duchen, so why won't the Royal Opera House or Glyndebourne touch them?

They were the very model of a 19th-century music drama -- or were they? Sky Arts is embarking upon a major series celebrating Gilbert and Sullivan, whose 14 comic operas enjoyed runaway popularity in their era, most of them selling out the Savoy Theatre for months on end. So why don't we hear more of them in the UK's mainstream opera houses?

WS Gilbert (1836-1911) wrote the words, Sir Arthur Sullivan (1842-1900) the music. They were as dynamic a duo as Lennon and McCartney – and much funnier – and are considered today to have paved the way for the development of musicals in the 20th century. The Sky series, though, is a much-needed boost: at present these very British musico-dramatic heroes are usually relegated to the fringes of operatic activity.

Increasingly "G&S" have been regarded as the preserve of university G&S societies and amateur dramatics, attracting obsessive boffins who know all the words by heart. Nevertheless many of Gilbert's phrases have passed into the national consciousness: "A policeman's lot is not a happy one"; "I've got a little list..."; "I am the very model of a modern major general..."

The British literary tradition being stronger than our compositional one, it seems fitting that the UK's most successful 19th-century operatic team placed the emphasis as much on words as on music. G&S's calibration of the two is well-nigh perfect, Gilbert's satire shining through the sparkle of Sullivan's catchy creations.

Some, admittedly, regard G&S as dated and the faux-Orient of The Mikado, one of their most enduring hits, as silly and patronising. But look past the surface: The Mikado satirised British politics, not Japanese, so it's meant to sound silly – that's the point. When G&S's comedy updates well, it does so spectacularly. In that sense it's more "relevant" than much other opera, which is not generally noted for user-friendly scenarios.

There's a bigger problem: in the operatic world it seems that if you're funny then you can't be taken seriously. History is peppered with tragic cases of composers who dared to confuse the serious with the humorous, the supposedly artistic with the way-too-popular. Operetta- light, or comic opera, became a valued tradition in its own right, its chief exponents including Johann Strauss, Offenbach and Lehár. But it was usually relegated to separate theatres such as the Volksoper in Vienna and the Komische Oper in Berlin, as if someone might otherwise think it was getting above its station.

Fine composers rarely judged operetta so harshly. Brahms adored Strauss's waltzes. Puccini was friendly with Lehár. They knew that musical quality isn't always determined by high-minded obscurity. Take Strauss's Die Fledermaus or Rossini's Le Comte Ory, which involves nuns in drag and a risqué three-in-a-bed episode: irresistible melody, vocal virtuosity and brilliant orchestration are conjured to accompany utterly ridiculous plots.

So it was with G&S. Gilbert created a topsy-turvy world where absurd premises are carried to conclusions consistent with their own bizarre logic; Sullivan's entrancing scores set them off to a tee. The Pirates of Penzance, HMS Pinafore and Iolanthe are some of their off-beat masterpieces.

G&S enthusiasts are everywhere. Mike Leigh made a film, Topsy-Turvy, about the duo. The late Sir Charles Mackerras, the conductor who restored the reputation of Janácek, was a devotee. And the tenor Toby Spence told me that as a student he once sight-read the percussion part in a G&S performance only to discover later that Sir Georg Solti was present, being a closet G&S fan.

It's time we appreciated G&S a little more as the national heroes they are. English National Opera had a smash hit with Jonathan Miller's production of The Mikado. Couldn't Covent Garden or Glyndebourne score similar successes? The best of these operas are no worse than some Italian opera buffa. But maybe they're too English, too funny and too popular. Is that not good enough? As Gilbert might have said: piffle!

'Gilbert and Sullivan: a Motley Pair' screens on 22 September at 8pm on Sky Arts 2