JimBall: With respect, you are over-analysing my phraseology. When I say "less likely to crash" I am of course referring to the fact single engine aircraft are not permitted over central london.
My original curiousity was to ascertain if private heli flights are permitted special exceptions in the heathrow zone, how this is arranged, and if there any practical differences between the exemptions process for helicopters and the process for fixed wing. Question answered anyway, thank-you.
I may well be rusty on certain aspects of air law, I did it 12 years ago! Thanks for pointing that out anyway.
Anyway, I'll sign out on this thread before it descends into an unnecessary but typical Pprune slanging match.