This morning I moved the master socket slightly - the Openreach engineer had screwed it to the skirting board, but this made it stick out too much and get in the way of some new blinds I put up the other day, so I disconnected it all and moved it up a few inches onto the wall instead - now the blinds open and close without problem.
While I was disconnecting it, I noticed a 2nd pair on the incoming cable, and vaugely recall discussion on here as to merits (or otherwise) of grounding them to act as a sort of screen, or perhaps to attenuate any ability of this spare pair becoming an aerial. My incoming cable runs a reasonable distance from a pole.
I checked with a meter that the spare pair wasn't connected to anything - no circuit or voltage across the pair, no voltage or current from either wire to ground.
I stripped the ends of the wires, twisted them together, and twisted on a 3rd wire which I connected to ground.
The result :
Nothing, really. It all still works, but no speed increase. There's
possibly a slight reduction in CRC and FEC error count, but...
Oh well. I'll carry on waiting for fibre....
Ian