Thanks Cameron.
Gerry, this was a test of many things.
1. ISO high...
2. Canon wireless TTL (Finally a consumer level Canon camera can control a Canon flash wirelessly without any donations to Yongnuo or similar; Truely inspirational and a world first)
3. How long before I cracked on a very very rainy day
I photographed the scene with flash first and dragged the car backwards to create movement. The ambient and flash was balanced to allow enough ambient to blur the car.
Apparently Canon engineers couldn't make rear curtain work on their TTL...
Bless those geniuses.
The rain filter couldn't be added in-camera so
PS it in.
Oops there is no EXIF on this? I think LR must have stripped it. I will post again.