Digital music crossed a major milestone last night when the first download-only single took the coveted number one slot.

The track - 'Crazy', is a collaboration between Grey Album-famed DJ Danger Mouse and Atlanta singer Cee-Lo under the band name Gnarls Barkley.

It's the first time a track has charted in the UK solely on the basis of download sales. It's been made possible through recent chart rules changes implemented in response to booming digital music sales which allow digital-only singles to chart.

Until recently a single's digital sales only counted toward chart position if the track was also available as a physical release. Now in the UK downloaded singles can count to a chart position as long as a physical release is made available the following week.