Home movie sketch show I Say I Say I Say (1964) by Peter Sellers, featuring Lord Snowdon (Antony Armstrong-Jones) and his then-wife Princess Margaret, Britt Ekland (then Mrs. Sellers), and financier and publisher Sir Jocelyn Stevens and his wife Jane Stevens (lady-in-waiting to Princess Margaret). The film was shot on the grounds of the Stevens residence.
h/t: Mike Springer
“In search of the hidden Sellers, Jasper Rees, The Telegraph
“I Say I Say I Say: A Delightful Home Movie by Peter Sellers (1964),” Mike Springer, OpenCulture.org