This is the "down and out" eye syndrome. It is characterised by ptosis, a down-and-out pupil, mydriasis, absent light reflex with intact consensual constriction of the opposite eye, and failure of accommodation. Classically, this is the lesion which develops during uncal herneation, due to an ipsilateral cerebral injury. Question 26.2 from the second paper of 2011 and Question 27 from the first paper of 2019 discussed the localisation of a midbrain lesion by a CN III palsy.
Cannot be nuclear: (authoritative source!)
Must be nuclear:
In addition, the college in their answer to Question 27 from the first paper of 2019 mention that "A mass lesion results in pupillary non-reactivity, in diabetes the pupil is spared". This is accurate: diabetes and other forms of microvascular disease cause a pupil-sparing oculomotor palsy. This is because the nerve's central core underoes ischemic infarction.
Walker, H. Kenneth, W. Dallas Hall, and J. Willis Hurst. "Clinical methods." 3rd edition.(1990).Chapter 60 Cranial Nerves III, IV, and VI: The Oculomotor, Trochlear, and Abducens Nerves - by J. Donald Fite and H. Kenneth Walker.
Twenty five years out of date, but still relevant.
These authors, in turn, reference even more ancient vellum:
Leigh RJ, Zee DS. The neurology of eye movements. Philadelphia: FA Davis, 1983.
Miller NR. Walsh and Hoyt's clinical neuro-ophthalmology. Vol 2. 4th ed. Baltimore: Williams and Wilkins, 1985.