On Sat, 3 Sep 2016 04:19:49 -0700 (PDT),
wrote:

On Saturday, 3 September 2016 10:30:55 UTC+1, T i m wrote:
Fishing around I found what could have been the partner end of another
plain cut cable, exposing some insulated (blue / brown) copper
stranded cable in a flat-oval black outer sheath.
The lampholders look like std size (ES / BS) hampholders but with
rubber collars where the lamps go into the holders (suggesting they
were 'supposed' to be 'outdoor' lights).

festoon lamps
https://www.essentialsupplies.co.uk/...holders-1.html

Ah! Yes, that looks like them. ;-)

You can buy the festoon cable and the lampholders separately; the lampholders fit over the cable with insulation piercing connectors

So when they advertise them as 'rewirable' (where one might normally
consider a screw terminal of some sort), these simply differentiate
between those and 'pre wired / moulded' alternatives?

A rubber cap if adhesive-lined and heatshrink should be reasonably safe in domestic circumstances for the end.

Ok ... whilst I guess it would, I'm surprised there isn't a more
'mechanical' end, considering that it's out in the elements?

So, if the lampholders are IDC (into a continuous run) and / or then
sealed ... I'm guessing I couldn't then use one to join an
accidentally cut cable for one and would have to seal it from the
elements for another?

"The lampholder is not waterproof, so the joint to the cable is not
waterproof, if you use the rubber sleeve water can get trapped between
the lampholder and the lamp. For outside use we do not recommend these
loose lampholders, use the traditional moulded festoon see here unless
the joint is made using a sealant.
If used in damp environment do not use the rubber sleeve so the
lampholder can vent and keep dry."

So ... if what I saw was an accidentally cut cable (and by looking at
the discolouration of the copper ant the ends, may have been done a
while ago) he / I really would need to re-join the wires mechanically
first and then ensure they were fully waterproofed after that? A two
core, 2.5 mm^2 waterproof junction box? I guess that might be the sort
of thing that would also be used for joining a cut electric lawnmower
cable.

Cheers, T i m