James and Oliver Phelps (Fred and George Weasley) will be attending the Thames Festival in London, England this weekend.  They will be showing behind-the-scenes footage from one (or more) of the Harry Potter films.  It is not certain what films will be used.

It is on September 13-14 in the Jubilee Gardens near the London Eye, which is open to the public.  If anyone goes please send in photos or a report!