16:00The Official Chart on Radio 1 with Jack SaundersGreg James sits in for ReggieBBC Radio 1 Duration: 3 hours Sun 25th Mar 2012, 16:00 on BBC Radio 1 N. IrelandListen or watch as Greg counts down the Top 10 to reveal the UK's new Official No 1 with all the videos streamed live online at bbc.co.uk/radio1.GenresMusicPop & ChartExperimental & NewEntertainmentBrandThe Official Chart on Radio 1 with Jack Saunders Source: BBC Online