Olive, thank you for the link to past posts on VFR, from which we get the MOD's version (to the Mull Group):
"The Board members concluded that the prevailing weather conditions were such as to demand flight in accordance with Instrument Flight Rules (IFR) in the vicinity of the Mull of Kintyre. The prescribed minima for flying visually, VFR, are horizontal visibility of 1 km beneath a cloud base of at least 250 feet, if flying below 140 knots; and a visibility of greater than 5kms, 500ft minimum cloud base, and 1500 metres horizontally from cloud, if above this speed.
which you confessed yourself content with at #4576. Thus it would seem that "flying too fast" would imply an IAS in excess of 140kts. Messrs W&D were obviously of the opinion that was indeed the case, as they seemed to suggest to the HoL that conditions could well have been VMC before waypoint change as compared to "the vicinity of the Mull of Kintyre" requiring IFR as above. Other than the "modelling" by Boeing, why should there be reason to believe that IAS was indeed above 140kts? Other than suggesting that to gainsay the RO's findings is absurd, is it not true that as ever we just don't know what their precise IAS was?