dogle,
Your:
".....a few minutes after departure from Heathrow of the shaken voice of a KLM Captain announcing "I hope that you were not upset by the unusual noise - I had to use the reverse thrust to comply with a, ah, very urgent request from Air Traffic Control....."
OMG - is this standard operating procedure in the air?
The divebrakes
can be opened partially - but
not delicately ! It's hit and miss. You just get more or less of the same effect - no nose down, no loss of speed - just an enormous increase in the rate-of-descent !
Danny.