A celebration of the biggest-selling singles of 1999, with contributions from Blur's Alex James, Steps' Lee Latchford-Evans and Hannah Spearritt from S Club 7. It was the era when the Vengaboys were partying hard, Christina Aguilera had a Genie in a Bottle, and Ricky Martin was Livin' LaVida Loca, but who had the biggest-selling single of the year?