"the most likely place for a midair was overhead an uncontrolled airfield."
They should have told the CAA.
I agree totally; the OHJ is a stupid idea, dating as it does from pre-radio WW1 signals square days.
What we need is WW3; then the CAA could update the syllabus to WW2 and
they had radios in WW2
Sadly, with the nuclear deterrent in place, we aren't likely to get that option (despite some peoples' best efforts) so aviation will just have to make do....