To understand why Gordon Brown abandoned his plans for a general election, you need look no further than Andrew Murphy, a project manager from Crawley in Sussex.

Mr Murphy, 32, is not only a lifelong Labour supporter who plans to switch sides after the Conservatives' pledge last week to raise the inheritance tax threshold to £1million. He also lives in the most marginal constituency in the country.

In the 2005 general election, Crawley's Labour MP, Laura Moffatt, scraped through with a majority of only 37 votes. She subsequently had the momentous number tattooed on her foot - a black 37 over a Labour red rose.

If Gordon Brown had called a snap election, it would have required only 19 swing voters like Mr Murphy for the Conservatives to recapture Crawley. And if a few dozen other marginal constituencies followed suit, the Conservatives could have taken the country.

There is no doubt that the Conservatives' inheritance tax promise was a vote winner in Crawley, a compact commuter town 28 miles south of London. House prices in its ever-expanding suburbs have soared in recent years to more than £400,000. The prospect of a £1million inheritance tax threshold has caused Crawley residents who previously voted Labour without a second thought, to think again. “The inheritance tax suits me well,” said Mr Murphy. “We already pay so much tax and I think Gordon Brown is responsible.”

And, he added: “Labour's had long enough. I have no confidence in the leadership anymore.”

Hayley Young, 22, giggles and grimaces when asked about politics. By her own admission, she is not that interested, but mention inheritance tax and her face lights up. She knows exactly what the Conservative policy promise would mean for her and she likes the sound of it.

Helen Hamilton, 61, has a family to worry about. “Who wouldn't want not to have to pay inheritance tax?” the mother of two and grandmother of four questioned. “We're taxed so many times. They've got to help middle-class families.

“It's absurd. If we don't change things soon, we'll all be emigrating!”

Chris Francis, 19, is another dithering voter with an eye on his inheritance. “Inheritance. Yeah. That's good," he said. “I'm just hoping I won't have to use it too soon.”

And when Peter Jefferson, 51, votes Conservative in the next general election, it too will be a vote for the policy, rather than the party or the politicians. “I was born in a council house and I worked my way up,” said the executive. “Why should we have to pay for moving up in the world?”

Most delighted of all about the Conservative's pledge is Crawley's Conservative parliamentary candidate, Henry Smith. A short man with big blue eyes and a floppy blond fringe, Mr Smith knows his party is on to a winner. “I was out canvassing this morning and on the doorsteps, we had only two people who said they would vote Labour,” he said, as if he couldn't quite believe his luck.

“These people can hardly be called wealthy individuals,” he said. “They're not sitting on landed estates. They've worked hard to pay their mortgages and they deserve to able to pass on their assets.”

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