Quote: LF13 "Clearly, there is a difference between being overtaken before you make the manoeuvre and someone overtaking you whilst you are the process of manoeuvring. However, fault can only be determined from the exact circumstances and evidence of any individual case.'"
Only an utter moron would START overtaking you AFTER you had started to turn, though. But even if it did, your problem would be that, as you (by definition) never saw the overtaking motorcycle, then you cannot possibly give evidence that that is what it did. You won't even know that that is what it did. You would only be assuming.
Also, if you knew that the motorcycle was behind you, and if you truly did check your mirrors before turning, then it's hard to see how you could fail to be aware; if the motorcycle is no longer behind you at that second- let me think, where could it be?