The boundaries are a bit of a mystery. Sometimes they make sense but quite often they don't. They frequently meander around with no apparent regard for development or geography and occasionally they rampage across the landscape , cherry picking specific locations for no apparent reason. Perhaps there are logistical requirements, spreading out the workloads of the poor beleaguered posties. Or perhaps it's all a big Post Office in joke. Who really knows?
You do have to ask yourself, just why it is necessary for Hyde Park and Kensington Gardens to be in five different postal districts? Surely, it would have made sense for the boundary to follow the perimeter of the parks. It was hardly going to tax the resources of any one district, but no, the parks are unevenly divided between W1, W2, W8, SW1 and SW7, with the lines curving and twisting through the parks. The Serpentine, for instance, largely belongs to W2, but SW7 takes a bite out of its southern shore. The main north south boundary on the western side of the parks deviates to take most of the Round Pond into W8 but still manages to leave part of it behind in W2!
There are examples of this strangeness all over London, if you care to look. In reality, of course, it makes very little difference to our lives, but it is nice to know that this City so often seems to find a way to avoid conforming to what most people would consider to be logical…………….and I like that!