I've seen this excellent documentary a few times - most recently today - and have thoroughly enjoyed it and been completely interested each time.

The beautifully shot documentary, released 2014, chronicles a year in the life of 39 acres Buckingham Palace Gardens. The gardens' evolution throughout the centuries, the diverse, thriving plant and wild life, the seasonal transformations, and the urban oasis' Royal uses, are explored. (If this paragraph seems somehow very familiar, it's because I'm who also wrote and added the production's Overview description to TMDb.)

Highly recommended.