Cant answer that one Mike - it might be that the original design originated in the states / Canada, and the British one is a variant on that theme.

They do look very impressive when you stand alongside one and as I say the picture does it no justice at all.

Further down the line from where I took the picture there is one of these pylons just a few yeards away from the road so I had to stop and take a close up / personal look.

They are also dismantling some of the old style pylons nearyby guess this new line makes them redundant.