Could it be one of those deliberate "enhancements"? After all, I
doubt that Gravesend has much going for it (what an unfortunate name
in any case) so the locals might want to make the most of what they do
have.

I am reminded of the (perhaps apocryphal) story that at Eastbourne the
sunshine recorder used to be right on the seafront where it could
catch the very earliest and the very last rays of the sun and so
apparently give Eastbourne more sun than neighbouring resorts.

So perhaps Gravesend might have more than one recording station, the
official one and the publicity one.

Jack