HWD,
Exactly, there is NO simple answer.
To be fair, a glider or microlight wouldn't be able to carry out the manoeuvre that nearly killed me and the 5 others in the aircraft that day.
Hence my suggestion on the other thread:
"Just to set the cat amongst the pigeons, how about making Mode C mandatory for aircraft transitting under the London TMA unless able to obtain at least a Radar Information service?"