.
IMHO the post by
stiknruda puts this 'incident' into sensible perspective - as some others have earlier.
GBOACdave
What I'm trying to say is, this term 'criminally negligent' seems to be a catch-all these days for anything that could annoy someone else.
I agree.
The term is much over-used - and almost always misused.
Cows getting bigger
From the ANO (which I believe is
law 
)
Articles 73 and 74 used to be the law. The equivalent articles of the 2009 ANO are 137 and 138.
NB: I'm simply correcting your errors re the law -
not agreeing that either 137 or 138 would be appropriate in circumstances such as those alleged by the OP.
I'm sure some highly paid suit from Holborn could whistfully make a mockery of the Regulator in the courts.
Overkill.
A bargain price moderately experienced aviation barrister could do the job perfectly adequately if (which I doubt) the Regulator was silly enough to prosecute pilots for Endangering in circumstances such as those alleged by the OP.
FL
(Formerly a 'highly paid suit' from the Temple - who used to do this sort of case for fellow aviators for a modest fee or FOC.)