The Department for Tranport sent a fact sheet yesterday which suggests if a kayak extends 1-2m from the rear of the vehicle, then the "end must be clearly visible". Does this require lights at night? I e-mailed back.
As I suspected, the definition of "clearly visible" is ambiguous. This is the reply in full.
Dear Mr Willis
Please find attached our fact sheet which summarises the regulations relating to overhang on vehicles.
The Regulations do not specify the type of warning required if the projection is between 1m and 2m - it only requires that the projection shall be "clearly visible to other persons using the road within a reasonable distance, in the case of a forward projection, from the front thereof or, in the case of a rearward projection from the rear thereof and, in either case, from either side thereof."
DfT - Transport Technology and Standards
Now someone from the forum is trying to find out more.
Early start tomorrow - I'm flying to Spain tomorrow until Sunday to help my poorly old Mum move out of an old folks home and back into her house.