Free entry to the park for the day, first come first served. Also get the chance to play the upcoming Wii party by Nintendo. Performances from Jedward and Alexandra Burke. Up to 4 tickets per claim.
"A ticket will entitle you to FREE entry to Chessington World of Adventures on Saturday 9th October between 10am to 5pm, plus an evening of entertainment, courtesy of Nintendo"
Check Junk Mail for Ticket confirmation, that's where mine was.