The Heath ponds are fed by rivers that used to flow through London but are now underground. This swampy pond is actually the lake in St James’ Park. It used to be a marshy place where the River Tyburn flowed down towards the Thames. Nash landscaped it when Buckingham Palace was built. You can just see it in the background of this photo taken this week on my way to the Royal Society. I certainly couldn’t swim in all that weed and neither could the ducks.