Can’t recall where I came across this – but I’m glad I did.

Mastermind specialised subjects
The following specialised subjects have appeared on the programme:

Aztec Mythology
The Life-cycle and Habits of the Honey-Bee
The Moomin Saga by Jove Jansson
Notable British Prisoners
Burial Grounds of London (taken by the 1981 champion, Leslie Grout)
The Vampire in British Fiction
The Eleventh-century Japanese Tale of Genji and Lady Murasaki
The Buddhist Sage Niciren

While the following were rejected:

Routes to Anywhere in Mainland Britain by Road from Letchworth
Orthopaedic Bone Cement in Total Hip Replacement
The Development of the Self-service Petrol Station, 1963-68
Cremation Practice and Law in Britain
Chicago Gangsters of the Prohibition Era – Christopher Hughes proposed this one, but the producers felt it wasn’t sufficiently well-documented.
The History of the Existentialist and Phenomenological Philosophical Movement
The Banana Industry
The History of St. Andrews University
The Managerial Career of Brian Clough – rejected during the Magnusson era, though “The Life and Career of Brian Clough” was eventually used in 2016.
Meteorology for the Private Pilot Licence
History of the World Since Jesus Christ – rejected for being, in producer Jon Kelly’s words, “a bit broad”.
History of Europe Since Jesus Christ – proposed by the same person after the previous subject was rejected.
The History of Loganberries
Perfect Squares to 992 = 9801
Diamonds are a Girl’s Best Friend (as Everybody Knows)
The Natural Life of the Goldfish

I particularly enjoyed the juxtaposition of

The History of the Existentialist and Phenomenological Philosophical Movement

with

The Banana Industry