Richard Bellamy was a British politician in the early years of the 20th Century, as seen in 'Upstairs, Downstairs'. Although he held the title of 1st Viscount Bellamy of Haversham, it wasn't hereditary, but rather from a combination of his hard work and his wife's family connections. (Lady Marjorie Talbot-Carey Bellamy was the daughter of the Earl and Countess of Southwold.) Richard Bellamy was of simple origins, being the son of a poor parson.
Or so he thought.
Based on his incredible similarity in appearance to Gerald Christian Wimsey, it is the conjecture of Toobworld Central that they are half brothers, each unaware of the other's relationship to themselves. And we're going to maintain that their common father is the 15th Duke of Denver, rather than to cast aspersions on the good - yet unknown - name of the country parson who was father to Richard Bellamy in name only.
Although we never meet the father of Gerald, Peter, and Mary in the televised mysteries, it's not hard to believe - when it comes to the wandering eye - that the tree isn't too far from the apple (as it were) in the Wimsey family. In "Clouds Of Witness", Lord Peter Wimsey finally figured out (long after the audience!) why his older brother the Duke was so reticent in providing an alibi for himself: a young woman was involved. So it's a case of "like father, like son". And Lord Bellamy, even though he never knew his biological father, was cut from the same cloth, as seen in his show. I've been enjoying the practice of dedicating these theories of relateeveety to my friends, so this one is going out to that Master Wold Newtonist, Win Scott Eckert....