"Anyone who even considers flying in thick fog is an idiot."
That's me then, (and instructor, Flt Lt N. R...H)
When we positioned for first take off on my 2 day FHT (final handling test) on the RAFSAR Seaking course, at Culdrose, we had to ground taxi as there were insufficient references to air taxi, due very thick fog.
(with diversion fuel for Heathrow)