BUNHILL : Elvis Presley wrote this column

Have you heard the rumour about the British drugs giant that's going to be swallowed up by a competitor? Stock market observers certainly have - time and time again. For more than a year, the City grapevine continued to tell us that the Swiss group Roche had Zeneca in its sights, and then Roche went and spoiled it all by buying a German company instead. I say "spoiled", but in fact the fun was only just beginning because the rumour machine swiftly shrugged off the disappointment and installed Glaxo Wellcome as the latest hot tip to launch a takeover bid, rescuing Zeneca's share price in the process.

Gossip is the lifeblood of City dealers, who need to make a market in their share portfolios so that they can offload stock to institutional investors at a profit. Sometimes their information will come from a reliable source, sometimes it will be pure conjecture, and sometimes it will spring from the tired and emotional ramblings of a fellow trader shortly before he's carried from a City curry house in the lying-down position. But regardless of whether the rumour has any basis in fact, as long as it seems halfway plausible and enough people want to believe it, then that share will be "in play" and investors will flock in hoping for a takeover bid.

With the advent of the silly season, when action takes a break and gossip fills in the gaps, we can expect plenty more of this - particularly in the financial sector where, we are told, banks will be merging with each other to combat the battalions of building societies switching to public company status. But the real merger activity this summer, as in every summer, will be between fact and fiction, so it seems a good time to speculate about speculation.

For instance, the hot stories in pubs and offices last year concerned a "gay" Cabinet minister and a Premier League footballer with an "ecstasy habit". At first, the momentum behind these rumours was supplied by the fact that you'd heard them independently from two people who'd never met - so there had to be something in them. Then you'd talk to someone else and they'd heard the same things. And before long nearly everyone you came across was recounting the stories, with more and more embellishments and more and more certainty as you went further down the line. There was no proof, but that was just a detail; everyone had heard the rumours so they had to be true.

The logic seems persuasive enough until you consider how jokes do the rounds. For example, there's the old one that goes: "Who's the most unpopular football fan at Borussia Monchengladbach ... the one who shouts 'give us a B'." Thousands of people will have heard this joke, but no one to my knowledge has suggested that it was based on close observation of German spectators, scrutinised by a panel of expert pundits and then verified by the club itself. Instead it's just possible that the joke, like many rumours, sprang from the imagination of one person and then travelled round the country without holding a single grain of truth.

So proficient is speculation at feeding upon itself that I'm willing to bet someone out there has invented a boomerang rumour. He's told a few friends, say, that Big Frank the Friendly Family Butcher is about to make a bid for the Bank of England, and then he's forgotten all about it. In the meantime, the story has fanned out through friends of friends, acquaintances of friends' friends and colleagues of acquaintances' acquaintances before eventually making its way back to him. "Knock me down with a feather," he says. "I thought I'd made that one up."

The soul singer Marvin Gaye knew a thing or two about speculation. Indeed he sang about it in his lament on romantic betrayal, Heard it Through the Grapevine. But had he had a stronger grasp of the rumour mill, his lyrics would have gone as follows:

I bet you're wondering how I knew/'bout your plans to make me blue/From two other guys you never knew/And so I know it must be true.

IT'S BONANZA time on the buses, with around 780 drivers and conductors poised to collect windfall payments of up to pounds 27,000 when Metroline comes to the stock market later this summer. The company, which runs a fleet of more than 400 buses in north London, handed out free stakes to its workers when it was privatised three years ago, and now it's not their bus but their ship that's coming in.

Windfalls like this should be a cause of unqualified rejoicing, but it may be that some of the crews take a slightly more downbeat line: "27 grand? Are you taking the mickey? Now either give us the right money or get off the bus."

Well I do declare

SO YOU'RE still sitting on it, aren't you? No, not your chair, your tax self-assessment return - that form the Inland Revenue has sent out to all people who are or were once self-employed, even if it was for one day only in the long hot summer of 1637.

Your procrastination is understandable. After all, you've got until the end of September to send it back, you might as well leave it for a rainy day, and you've got to fill in all those confusing coloured boxes denoting things you've never come across.

Always remember, though, that the taxman values honesty above all other things, and as long as you play it straight you have nothing to fear. Just to demonstrate, here is the kind of honest self-assessment that should stand you in good stead:

"Failed to fulfil my early promise and could have done better at Chemistry. But I was always good to my Mum, I've got two lovely kittens and, all in all, when all's said and done, I'm a decent enough chap and I always give to charity. Any chance of a rebate, then?"