Keston windmill

I thought there were 4 windmills in the London area, but I recently heard about another, at Keston. Keston used to be in Kent, but is now in the London Borough of Bromley and within the London bus routes.

I went to visit but was disappointed to find the windmill was immediately behind a high hedge and trees. So I could see very little. It is privately owned, presumably by the nearby house, Mill House.
I was then disappointed to find that I had missed the 2019 open day by just one week! It was open on 11th and 12th of May, and I went there on 20th! And they don't seem to open every year.

Wikipedia says the windmill was built in 1716 and is now Grade I listed. It is a black post mill.

Some historic photos of Keston Mill. And the "official" page on the mill.