This is the River Tyburn.
And now it's channelled through this great Victorian sewer,
but it still follows its ancient course,
right beneath Buckingham Palace.
And it provides a fascinating glimpse into the past,
because this river made the land above boggy and marshy,
with pools of smelly, stagnant water.
Not exactly what you'd call prime royal real estate.
Until one king decided it might be useful after all.
Henry VIII, who came to the throne in 1509,
was a man passionate about the chase, for women and deer.
For Henry,
the swampy land on the banks of the river Tyburn was perfect for hunting.