"A very large chunk of some very busy airspace" Plain enough?
If these 'trials' are really so vital, why not do them in St Kilda or somewhere else in the middle of nowhere. Why must they be done in S Wales?
Oh - of course. It's cheaper for the mad boffins.
Really bŁoody handy to have 'cease jamming' phone no.s! What is the 'cease jamming' safety frequency?