I used to live in Harrow, which is in the north-west corner of London, around 8 years ago. I now have cause to frequently visit Harrow and on one such recent visit I noticed this sign.

Harrow, London. Or Harrow (London). Harrow obviously now feels the need to explain to all that it is, in fact, in London. I am thinking that I once thought that Harrow was quite happy to blur the boundaries, that it had some benefit from not quite being London.
I wonder why it now sees it important to explain it is a part of London so explicitly.