Never again will anyone be able to say that the UK's top 40 singles chart is made up of just record sales.

This week the Gnarls Barkley single “Crazy” became the first track to become number one through downloads alone.

The song, used in BBC ads for Zane Lowe's Radio 1 show, has been downloaded more than 31,000 times on all internet sites, a spokesman for HMV said.

Although officially launched in record stores today as a CD single, the song, which is by producer DangerMouse and hip-hop artist Cee-Lo didn't need the help of the high street to top the charts by outselling every other song available.

Until recently download sales have not been able to be included in the chart until a physical CD has gone on sale in the UK.

The rule had been insisted on my major retailers for fear that online sales may completely remove the urge to buy in store rather than online.

However last month the rules changed, meaning that as long as a physical copy was released the following week downloads could be included in the ranking.

Had the rule existed when Coldplay launched its single “The Speed of Sound” that would have been the first download-only number one.