This is the Putney river bus hard aground earlier this week. It was stuck on a mud bank for 20 minutes or so, blocking half of the river, prop churning white foam, turning grey waters brown.
If this were to happen during the Queen's Diamond Jubilee 1,000 boat parade it would be bad.
The Thames Barrier is meant to be raised during the pageant to ensure sufficient water but will it be enough?
At low water the Thames isn't that deep - see here and here for more information.
