Thank you to both chempat and nottsgirl1 for the welcome to rootschat and such quick responses to my query.

Thank you chempat for the link to the history of the asylum. It is very interesting reading, and somewhat reassuring re: the conditions and amenities there. I find it rather astonishing that it became so overcrowded so quickly, however I guess it served a large area. I haven't yet located the Nottingham Borough Asylum in the 1911 census but will try again at the library, and include variations of his name, which was often mistranscribed over the census years.
Thank you nottsgirl1 for your very kind offer to check at the Nottingham Archives. I forgot about the 100 year rule of course, but, as you say there may be something from his 1902 (patient #313437) or 1906 (patient #18965) admissions. Fingers crossed. I just find it so sad that he spent the last 20 years of his life there.

Again, thank you so much for your help.
WarBrideDaughter