I was at Cape Town international today.
Spoke to the ground engineers, and they mentioned "their quote"
The BA747 was advised of the situation by ATC after ATC had been informed by ACSA security of a person seen heading towards the aircraft whilst at the holding point.
ACSA security vehicle could not get closer due to the B747 with all engines running at the holding point.
ATC asked the crew what their intentions were...re the possible LMC/security issue.
the words replied with were to effect of "We will let LHR personnel deal with the problem if there is one".
and so the aircraft departed...ACSA vehicle entered the aircraft manouvering area after the departure, and continued the search, but no persons found.