Kayak Safety Flag Pt2

I'm still trying to reach a satisfactory understanding of how British law requires us to highlight our kayaks while in transit.

It was finding the New Zealand regulations which started me down this road. There have been some useful, but as yet inconclusive, comments on that post and on the UK Sea Kayak Guidebook forum.

I e-mailed the Department for Transport and today received a Word Document copy of its fact sheet. Sadly, it is also inconclusive.

ROAD VEHICLES (CONSTRUCTION AND USE) REGULATIONS 1986

REGULATION 82(7) - LOAD PROJECTIONS

If a load projects up to one metre, either forwards or backwards, no action is required.
If a load projects 1-2 metre forwards, no action is required.
If a load projects 1-2 metres backwards, "End must be made clearly visible. Para 4 Sch 12"
For details consult regulation 82 of the Road Vehicles (Construction and Use) Regulations 1986: SI 1986 No. 1078 as amended.

As most sea kayaks will project backwards 1-2 metres, then their "ends must be made clearly visible". What does that mean? High-viz markers like the Kari-tek one in the photo sent to me by Cailean? Lights at night?

I've e-mailed back to ask for a definition of "clearly visible"