The Create The World trading card promotion has started at Sainsbury's. For every £10 spent you'll receive a pack of four cards. There are 140 to collect. They are available until 13th June which means you'll need to about £70 a week in the store to obtain that number. Of course the chances of getting 140 unique cards from 35 packs is negligible so obtaining a full set is going to be expensive and involve a lot of trading.