There was absolutely no impact on the road wheels at all and nothing felt through the steering wheel, so not a pothole - just the downward thump. I have thought about it a lot and also feel the large red crane was too far away for any blast of air to affect us - even further away from the car ahead whose driver described exactly the same impact - we both felt something had hit the top of the car (as I said in the original post - he thought something had been knocked off his car), but, while enough to bounce the car, it was not that solid and no marks on the car - hence the blast of air theories (whether sonic boom, tyre burst or lightning). The closest explanation to what we felt was the sonic boom, but can find no reports of that over Nottinghamshire that day. Mystery persists!!
Ken. I still think my theory of a warp in the space/time continuum has some merit?

Bud
4/4 - Stanley