If you look at the first picture on

http://friendsofthornborough.org/

(Ta George!), I'll swear the lower part of the picture was exactly what I saw as the plane flew by although it was at a slightly higher angle. The fact that RAF Leconfield is nearby clinches it as far as I'm concerned. The clip of the aircraft could have been filmed at any time (library footage?) and added in for continuity and it's only megalithic anoraks that would have spotted the ruse ;-)

-Chris