Why is the pool at Buckingham Palace a secret?

1183.384 - 1206.338 PJ Vogt

The private house that our modern Buckingham Palace would be expanded out from, that first came into the royal family in 1761. In the centuries after, some of England's most notable architects would, in phases, transform this red-brick townhouse into the 830,000-square-foot behemoth that is there today. The story of that transformation is unspooled across the series' many installments.