I believe it is ACAS that make the rules? The Harrier can still overfly London, but it would have to be at a greater height. No Ram Air Turbine in a Harrier GR.7/9, etc. (The early Harrier had a RAT as did the Sea Harrier FRS.1). Hawk has better glide ratio and the back up of the RAT. It meets the requirements for ACAS. Something you would have to bring up with them.
It was debated during the 2007 25th Falklands Anniversary.
See John Farley's post at #91 on Harrier/P.1127.
http://www.pprune.org/military-aircr...niversary.html
It is a debate that crops up time and time again in relation to London flypasts. Can anyone provide a definitive answer?
TJ