Suck It & See Towing Mirror - CONVEX

The revolutionary "Suck-it-and-See" towing mirror was voted "Top Choice" by the Caravan & Motorhome Club magazine.
The only towing mirror to be moved by your internal mirror control and  you get a very accurate view of the road behind.
It simply fixes to your existing mirror using a suction cup
product has been tested to speeds of up to 120mph,
e11 approved

The following is direct from the UK Government Website

Towing mirrors the law

You must have an adequate view of the road behind you.

Fit suitable towing mirrors if your trailer or caravan is wider than the rear of your car.

You can be fined up to £1,000 and get 3 - penalty points for towing without proper towing mirrors.