It began as an anonymous two-line entry on the Internet, it was then elaborated upon by an obscure Japanese fanzine and has now become a simple, stark question: Is Noel Gallagher dead? The theory being posited is that the Oasis mainman died in a car crash last November and was replaced by a doppelganger so that the world's most popular rock band could continues its worldwide musical domination.

The rumours first began in Japan a few days after Noel's alleged "death" last year. They apparently stem from a number of leaks from the head office in Tokyo of Oasis's record company, Sony, where a high-level meeting of shareholders was convened after the "death". Oasis is one of Sony's biggest acts and generates millions of pounds in profits for the corporation.

Shareholders felt that if the news became public and the members of Oasis were to disband, the share price of the corporation would plummet and the Tokyo stock exchange would be thrown into turmoil. Some of the minutes of the alleged meeting, which have made their way onto unofficial Oasis pages on the Internet, show that shareholders decided it was better to install a "new" Noel in the band to steady the financial markets. Only the four remaining members of the band, their manager and selective personnel at the record company know the real story, according to the rumours.

For an unsubstantiated rumour, there are a lot of solid "facts" behind the claims. The story goes that when the band was recording its new album in the Abbey Road studios in London last year, Noel had a furious row with his brother Liam - furious even by their standards. Storming out of the studios, Noel elected to drive his top-of-the-range brown Rolls Royce (a Christmas present from his record company) back to his Camden home, despite the fact that he was in a highly emotional state. The car went out of control somewhere in the Swiss Cottage area and smashed into the wall of a private residence - killing the driver instantly and ending up in a small swimming pool in the house's front garden. The date is given as November 9th, 1996.

Once the decision was made to conceal the death, the problem faced by the remaining four members and their record company was where to find a suitable replacement for the dead star. The first problem was to find someone who looked so much like Noel that millions of fans worldwide, not to mention close personal friends, would be hoodwinked.

The second, and potentially more difficult, problem was to find someone with the same remarkable songwriting ability as Noel - the new "Noel" also had to be able to play the guitar, sing and talk in a convincing Manchester accent.

According to unofficial reports, the band and the record company first decided to replace Noel with one of the members of the Oasis tribute band, No Way Sis, but even though they could play all the Oasis songs note perfect, no member of that band had the required physical resemblance.

It was then decided that no one person could replace the "dead" songwriter, so a more imaginative policy was called into play - Noel would be replaced by two "new" Noels.

After weeks of research, the band's manager came across a Liverpool builder who had once won a Noel Gallagher lookalike contest at a Blackpool funfair.

His name is William Shears and with the benefit of some subtle plastic surgery and voice coaching lessons he was groomed over a period of a few months into the new "Noel".

For the song-writing side, the band turned to a close musical friend of Noel called Richard Ashcroft who fronts a successful band called The Verve.

The reason they turned to Ashcroft was because Noel had dedicated a song called Cast No Shadow on Oasis's second album, What's The Story? to Ashcroft, so enamoured was he of his friend's songwriting ability.

Ashcroft also plays all Noel's guitar parts on the new album as William Shears is still undergoing intensive guitar playing lessons to prepare him for Oasis's upcoming tour.

As "proof" of Noel's death and subsequent replacement, the Japanese fanzine which first printed the rumours devoted a special issue to the "Is Noel dead?" mystery, offering up this "evidence":

Oasis last played live just two weeks before Noel's "death". They then took an eight-month break from playing live concerts - despite being the most popular rock band in the world. Although the band members say they were busy recording their album, the fanzine says this short sabbatical was taken to given William Shears enough time to learn to play the guitar and all the Oasis songs.

Similarly, "Noel" didn't talk to the press for eight months - again very strange given his gregarious, voluble nature. When he did break his silence in the current edition of Q magazine, he spoke warmly and affectionately of his brother Liam - is this the real Noel speaking?

All the clues to Noel's "death" are contained in the lyrics on the new album. All the songs were written by Richard Ashcroft who, being both grief-stricken and suffering from guilt, alluded to the real story behind Noel Gallagher/ William Shears. Track three on side one of the new album, My Big Mouth, contains the lines "Everybody knows, but no-one's saying nothing . . . Around this town you've ceased to be, where angels fly you won't play, so guess who's gonna take the blame . . . I ain't never spoke to God, I ain't never been to heaven, but you assumed I knew the way, even though the map was given, and as you look into the eyes of a bloody cold assassin, only then you realise with whose life you have been messing."

The artwork on the cover of the new album (see above) contains further clues: the picture of the crashed Rolls Royce in the swimming pool is a blatant pointer to the manner of Noel's "death". Notice also how "Noel" is well back in the picture, his face obscured - is this because the artwork for the album was taken in March when Noel/William was still bearing scars from his plastic surgery?

There is also the strange case of the date on the cover of the album - August 21st, Thursday. The band members say it is there because it is the date and day of the album's release next week, but it is unheard of in rock 'n' roll history for any band to release an album on a Thursday. The charts are based on sales of an album from Monday through to Saturday and for this reason all albums are released on a Monday. By releasing their album on a Thursday, Oasis have only two days of sales to try and make the number one slot for that week.

Why Thursday? Why August 21st? Coincidentally, 30 years ago on Thursday, August 21st, William Shears was born.

Most damning of all, when the Japanese fanzine got their hands on a pre-release tape of the new album, they paid particular attention to the only song on the album on which "Noel" sings lead vocals, Magic Pie. They sent a copy of the song, along with a copy of Noel singing Wonderwall on the last album to a university professor in the US who analysed the "sonograms" of each song - this involves a computer analysis of the voice on both recordings. The professor concluded that the songs were sung by "two different people".

Some music journalists have claimed that if you play the fadeout to a song on the album called I Hope, I Think, I Know backwards you can just make out Liam saying "I buried Noel". By a remarkable coincidence, the date given for Noel's "death", November 9th 1996, is 30 years to the day since Paul McCartney apparently "died" in a car crash, thus prompting one of the biggest hoaxes in rock 'n' roll history.