The campaign against the new runway at Heathrow is doomed – and the organisers have only themselves to blame. From the moment they agreed to let a trad jazz band on to their open-top bus, their fate was sealed. They might just as well have painted a giant banner saying “This is a lost cause”, or announced a joint initiative with the South-West London branch of the Paedophile Information Exchange. For when the fat lady sings — or rather, when the fat men strum and blow – you know it’s all over.

Yet there the jazzers sat, pleased as Punch and twice as ugly, blasting out Heathrow Blues or Runway Rag, or whatever abomination they had composed for the occasion. To those hapless souls within earshot, the sound of a low-flying jumbo jet would have come as blessed relief.

Cometh the day, cometh the band. That is the iron law of public campaigning. No sooner is a committee formed, than the jazzers turn up like the bent coin in Humphrey Lyttelton’s Bad Penny Blues. And theirs is an offer that cannot be refused.

The musicians’ motives are easily deduced. It is egotism, not ideology, that drives them, which is why they will happily offer their services to anything from a church fête to a party political broadcast. Like hospital disc jockeys, jazz musicians love the sound of their own voice — or their own tubas, trumpets and slide trombones — and they will grab any chance to inflict their perversion on the innocent. Just as the phrase “Cheer up, it might never happen” is guaranteed to bring still deeper misery, so the sound of banjo-strummin’, tuba-puffin’, waistcoat-and-boater-wearin’ grandads whippin’ up a storm can be relied on to spread unremitting gloom.They are living proof that the Devil doesn’t have the best tunes — he has the worst ones, and he wants to share them with us, at top volume.

With a public approval rating that ranges from indifference (beer tents) through to outright hostility (crowded shopping precincts), trad jazz is in the doldrums. In its Sixties heyday, “UK Trad” received plenty of media coverage, notes one website wistfully, while in the Seventies, Kenny Ball “got occasional spots” on Pebble Mill at One. (Let’s hope he’s fully recovered.) These days, even the cable channels won’t touch it, and the future looks bleak for the likes of the Quayside Hot Stompers and the Antique 6.

In this climate, a dream gig is a keg of real ale and a plate of sandwiches. No wonder they are happy to play anywhere there is an audience, however impervious it may be to their relentless bonhomie. Fields, marquees and floats are their “stomping” grounds, where they root and toot to their hearts’ content, deluding themselves that they are contributing, in their own modest way, to the gaiety of the nation.

The jazzers’ relationship to their charitable hosts is classically parasitic. So while the parasite thrives on the public exposure, and grows fat on the free beer and sandwiches, the host is invariably laid low. Hello Dolly is nothing less than the death knell de nos jours, and its stripey-blazered performers are harbingers of doom, every bit as dangerous as those of mythology.

The Heathrow campaign is only the latest in a long line of victims. Down the years, the jazzers’ tours of duty have taken them from “Save the GLC” festivals to the ill-fated Millennium Dome. The result is always the same: abject defeat.

Remember Norman Willis? Thought not. Willis was the hapless leader of the TUC during the high tide of Thatcherism. He was last seen leading a bedraggled trade union march to oblivion, while accompanying a trad jazz band on comb-and-paper. Big Norm retired hurt soon afterwards, but the band played on.

It’s high time we called the jazzers’ bluff. To them, I say this. If you really support the causes you so publicly endorse, leave your instruments of torture at home. And to their neighbours, I say this. Selfdefence is no offence, and there isn’t a jury in the land that would disagree.