Could this have anything to do with the Rapide that crashed on a section of the M1 which was being built about this time.
I remember seeing the Rapide a few weeks before the disaster and being impressed with the fact that it had VP props (Proctor engines?).
As best as I can remember it hit an earthmover on take-off with several executives of the construction company on board and caught fire.
I shall have a trawl through my excellent Air-Britain Rapide book and see if I can find any more information.