This takes place today apparently. This post on the SWM Readers list has the entire post.

Concorde G-BOAF will depart London Heathrow at approximately 11:10am before heading out over the usual supersonic acceleration point. It will then go supersonic for the last time over the Bay of Biscay before returning to Bristol where weather permitting it may fly a low pass before landing at Filton at approximately 12:42.