Highway Code section on overtakingDO NOT overtake where you might come into conflict with other road users. For examplewhen a road user is indicating right, even if you believe the signal should have been cancelled - do not take a risk; wait for the signal to be cancelled
stay behind if you are following a cyclist approaching a roundabout or junction, and you intend to turn left
when a tram is standing at a kerbside tram stop and there is no clearly marked passing lane for other traffic

Can I just throw three pennoth in ?

Humans have a field of vision that is ALMOST 180 degrees, get someone to test yours, its actually quite surprising what you can see to the side of you, I already know what both of my eyes are like for field of vision because I have it tested by my doctor every six months, but a simple test such as getting someone to approach from behind and then holding your hand up when you can see then should surprise you.

Further to that, your vision is also alerted more by moving objects, its an animal instinct sort of thing.

So, a moped approaching your car from behind won't be visible to you yet, but if you turn your head even just slightly then your 180 degree field should pick them up easily, especially if they are deviating from a static location in relation to your eye, in other words they are pulling out to overtake and moving across you field of vision.

What we really need is an almost 360 degree field like some birds do.