One of the blokes I work with tows a caravan with a shogun and has just got a set of towing mirrors after one of his club members got a ticket and three points the other week for not being able to see behind clearly
I've searched and the only thread I can find that mentions it is this one
So do we need them or not
I know alot is going to depend on a the tow car
Copy of some text from a website selling mirrors
The Law in the United Kingdom specifies, you must be able to see clearly down both sides of the caravan, and see 4 meters either side of the caravan at a distance of 20 meters behind the rear of the caravan.
This in reality means, if your caravan/trailer is wider than the rear of your tow vehicle, you must fit towing mirrors to comply with the law. You can be fined up to £1000 and get 3 point on your licence for towing blind. (At exhibitions, we have met many caravanners that had received 3 points and £60 fixed penalty notices.)
On tow vehicles conforming to directive 2003/97 EC or sold after January 2007, the towing mirrors may project 25cms further than the widest part of the caravan. On tow vehicles pre dating this directive, the mirrors may project 20 cms further than the widest part of the caravan.
Since 12th of December 2005 it is a legal requirement that you have type approved (e-marked) mirrors on both sides of the tow vehicle.