The all powerful United World Chart, which collates sales figures on a global basis, has it down as the most successful song of 2007 (by a country mile).

It currently stands as the sixth most successful song of the last decade and broke the iTunes record for the biggest-selling debut single. It won a Grammy, has transformed its singer from a rather pedestrian r'n'b warbler into box-office gold, and provided Manic Street Preachers with their biggest radio hit to date.

Rihanna really should count her blessings that Umbrellawas pushed her way, particularly as she wasn't the first choice of singer, or even the second choice. It was only a campaign by her management team - a campaign bordering on harassment - that secured her unlikely meal ticket.

You see, Umbrella was supposed to be a global smash hit for Britney Spears.

The song was written 18 months ago by Terius Nash, Christopher Stewart and Kuk Harrell, all respected r'n'b tunesmiths. Stewart, who had written songs for Britney's In the Zonealbum, tried and tried to get the song to Spears but, he claims, was waved away by her management: "Her current state was a little bizarre - it just wasn't meant to be."

The trio were distraught. They knew they had a massive hit on their hands and really believed Umbrella would be the song to relaunch Britney and help her out of the abyss. The only other big name they could think of to record the song in her place was Mary J Blige, who had previously worked with Harrell. Blige was still enjoying huge success thanks to her Breakthrough album, and was at a bit of a career high.

But the very week in 2007 that they tried to get Umbrellato Blige was the same week Blige was nominated for eight Grammy Awards. To cover their bases, they also sent the song to the head of the Island Def Jam label. Blige's "people" loved the song but simply couldn't sign off on it until the singer herself had heard it - which she didn't because she was tied up with Grammy commitments. Island Def Jam moved swiftly.

"At the time, if you heard Mary's name and you heard Rihanna's name, you'd want to hold out for Mary," says Stewart. "Mary was coming off a big success and was nominated for all these awards, so the plan for us was to hold out and wait for a response from her. But Island Def Jam were beating us up over the song. They were calling every 20 minutes for the entire Grammy weekend and every time we saw them, they're just applying all kinds of pressure."

Island Def Jam wanted their charge, Rihanna to sing Umbrella, but the songwriters were dubious. They got her into the studio to record it anyway - still waiting for Mary J Blige to get back to them - and suddenly everything changed.

"When she starting singing the 'ellas' on the song, we knew we had reached a jump-off point," says Stewart. "You just knew your life was about to change if you had anything to do with the record."

Months later, Manic Street Preachers recorded their cover of Umbrellafor an NME giveaway CD. It was picked up by radio, went on to iTunes, and suddenly the Preachers found themselves on high rotation.

"It was my favourite record of 2007," says Nicky Wire. "It's just so razor-sharp. And who'd have thought a song called Umbrella would be number one all over the world? It's such an un-pop word. I love it when a record seems to come from another universe - and I just wanted to have a stab at it."

For the writers, the song was a one-off. "Everybody has their one record and their one situation," muses Stewart. "There are a lot of talented people out there, but not many of them get that one song. For us, Umbrellais the perfect storm."

Unless, that is, your name is Britney Spears, who reportedly bristles every time she hears the tune.