We were told it was the one on the left but I don't actually have any proof.
Our land registry plan is useless, the restrictive covenants refer to "t" symbols on the plan (attached) but they don't exist.
It was the least of our worries when buying but after living here a few years it would be nice to know! We have replaced the fence on the left and the rear fence as we have a dog so needed to keep him in our garden - but part of the fence on the right has blown down & I'm wondering again now...