Robbie Savage and Alan Shearer start Sport Relief challenge

Robbie Savage and Alan Shearer are going head to head, and buttock to buttock, in a Sport Relief challenge: The Battle of the Backsides, where they have to sit on 90,000 seats at Wembley Stadium, 45,000 each.

Seth Bennett, who is the resident 5 live MC for the event, was at Wembley as the whistle blew, signalling the start of the five day challenge.

For more information go to bbc.co.uk/backsides