*Visions of a drive-by jousting*
IIRC, if it overhangs the vehicle by a certain amount (2 metres?) at either end it needs a visual marker on the end to signify it.
I believe legally it has to be a type of fluro triangle, like the ones you get in break down kits. But you see fluro vests and old rags on the end of most vehicles anyway, so not sure how enforced this is, as long as its visibly marked.
*QUOTE* From askthe.police.ukhttps://www.askthe.police.uk/content/Q748.htm
The maximum overhang to both the front and back of a vehicle (includes trailers) is a tricky matter. The overhang which you can have on such a vehicle is 60% of the distance between the foremost axle and where the overhang is to begin. So, the allowed overhang to the rear would be 60% of the distance between your front wheels and where the overhang is to commence. For overhang to the front, this would be measured as 60% of the distance from your front wheels to the front of your vehicle. Any measurements from the front wheels should be taken from the centre of those wheels.
You should mark overhangs with a bright cloth.