I guess Crystal Palace from what winston1 said about only that transmitter carrying London Live, but will check later when TV is not in use. Typical signal strength is 25%-30% and signal quality is 100% according to the Humax box.
It's worth mentioning the feed from the aerial to the Humax box goes down 1 wire of the shotgun satalite cable built into the wall that was used when we had Sky+.
That looks like an Antiference TC 18A, not a current model, but a good aerial anyway all be it without a 4G filter. Could be old stock the installer had. However I could be wrong, it could be a look alike.