One of the best breakthrough acts of 2008 played to a packed crowd at the 4Music Stage.

Duffy looked as sweet as sugar in a little blue and white frock, blue shoes and a red hair-band, but she admitted to festival-goers she could not help herself as the swear words slipped out.

The Welsh blonde’s floor-fillers Rockferry, Warwick Avenue and long-standing number-one track Mercy were received well by revellers dancing away in the evening sunlight.

Stepping Stone, a new song with a melancholy edge, winded down the set.

Her soulful voice was perfectly in tune as she bopped about the stage - captivating her audience who just soaked it all up.

The talented songstress praised fans for being “a wonderful crowd” and turning out in droves to hear her perform.

She cheekily confessed to tens of thousands “this is my V cherry being popped right before you.”

This may have been her first V gig, but it is unlikely to be her last judging by her strong performance.

Duffy won the 2008 Song of the Year Mojo Award for Mercy, and was also nominated for Album of the Year and Breakthrough Act.

Her number-one debut album Rockferry has sold more than 700, 000 copies in the UK.