Melville, L. (1908). The Beaux of the Regency; Volume 1. United States: Creative Media Partners, LLC.
I am always amazed to find these characters in the annals of Regency history. The Baron, later Brother Mary Joseph, would be steeped in the struggles of European royalty during the French Revolution. He was remembered as courageous, then holy. But also, a bit eccentric.
The Pope would name him a titular abbot, and he would go on to publish numerous religious works.
His time in London was short lived, roughly a year and ten months, and he was known to be great friends with another known eccentric, Romeo Coates.
Dame Barbara Cartland never mentioned him in any of her stories.