There is absolutley
NO ATC reason why they could not have climbed to 3000ft after Wembley and routed out like one of your Northolt outbounds. (Or for that matter come in inside CAS and descend if VMC)
There have been a number of incidents with London flypasts in the last few years.
http://tinyurl.com/2avf8q OR
http://www.caa.co.uk/docs/423/02_07_...ed_airprox.pdf INCIDENT 143/06
More should be done to avoid risks like this in the future. They had planned to fly at 1500ft but the nav warning said SFC-2500ft (base of CAS of course!) Why not just say what they are PLANNING to do in the remarks?
I hope the rotary guys out of Denham (or wherever!) got some good pics. The only thing they perhaps should of done is be on the freq that was working the Reds. (Northolt 126.45 I guess)
Thinking about it, why not publish the intended freqs to give traffic a clue???
Finally, does a hawk fly out of the sky at less than 300kts???