Officers are particular keen to identify the rider of a cruiser-type motorcycle, possible a Harley Davidson, which they believe was travelling slightly ahead of the motorcycle involved in the collision.
Were you travelling in the area at the time? Did you see what happened? Perhaps you saw a motorcycle matching the description of the cruiser-type bike?
Anyone with information, or dash-cam footage, is asked to call 101, quoting 44210166661.
Alternatively, you can contact independent charity Crimestoppers anonymously on 0800 555 111.