I can't make this myself, but it sounds interesting, a free lecture on Tuesday by Alan Bond of HOTOL and Skylon fame.
Hydrogen Fuelled Pre-Cooled Jet Engines
by Dr Alan Bond, Managing Director, Reaction Engines Limited
Tuesday 03 June 2008
Public open lecture - All visitors welcome - No admission fee - No tickets required - Doors open 5:30pm
Organised by the Royal Aeronautical Society and taking place in the Lecture Theatre at 4 Hamilton Place, London W1J 7BQ.
See
http://www.acc.co.uk/raes/space/080603_Bond.htm for more details.