Rear View Mirror - auto??

[Tonych]

I may well have missed a thread on this, and even more likely just being dense. The rear view mirror on my MG4 Trophy has a button marked "Auto". Pressing it doesnt seem to do anything other than switch an illumination under the Auto label. I've tried to check in the PDG user manual but can't see anything. What does it automatically do?

 

[IanMK]

It dips the rear view mirror so that you’re not blinded by a car behind you at night (unless you turn it off).

 

[Tonych]

It dips the rear view mirror so that you’re not blinded by a car behind you at night (unless you turn it off).

Thank you. I guess I hadn't been followed by a car with lights on full yet.