Hi Ryan, and welcome to ECN.
Yes, that looks like 11kV coming in at the top. There are clearly two sets of fuse cut-outs on the secondary side. I would guess that those on the right-hand pole go to an underground feeder.
The 5th-wire arrangement used to be employed here in the past for street lighting. There may be a few places still using the system, but it's been a long time since I've seen it. Some old poles still have the fifth bracket/insulator on them, but in most cases the extra conductor was removed many years ago.
Whereabouts in Britain is this photo from?\
