Congratulations to Laurie Bracknell of Guildford, who managed to spot the six changes we made to the building below, the Hayward Gallery on London's South Bank. For the chance of winning a bottle of champagne, readers are asked to spot the deliberate alterations we've made to the building above, Will Alsop's Stirling Prize-winning Peckham Library. Clue: there are seven changes. Post your answers, to arrive by first thing Monday morning, to Ring the Changes, 151 Rosebery Avenue, London EC1R 4GB, or fax 020 7505 6701. The first correct entry pulled out of the hat wins the bubbly.