Who might have filmed this?

[TRC]

A white squirrel of that era? Colt aviation had some of those......

Can't remember which it was, a 355 I hope - for some of it at least. I do know that the stuff over London was a Cabair 355.

.....might have been an old mate of mine well used to hedge hopping in Sioux and Gazelle.....

Nope, the pilot was never a member of the UK armed forces.

Who ever filmed it did not have the benefit of gyro stabilised.....

It was a side-mounted 36" Wescam with a film camera in it. One of the first - if not the first - large-scale commercials shot in the UK using one. They toppled the gyros regularly - over the Forth Bridge was one occasion - and they used it in the commercial because HH liked the effect.