Can I be prosecuted for speeding if I was not driving the vehicle when it was flashed by a speed camera?
No - you can only be prosecuted for NOT informing the authorities who was driving your vehicle, and doing so exonerates you from any prosecution - assuming that it wasn't you who was driving, of course!
This forum post covers this subject in more detail.
This link will take to a recent example in the forums of how the “unsure of the driver” defence can work in practice.