Section 7(2)(d) [It is not discrimination if]

The nature of the establishment or of the part of it within which the work is done, requires the job to be held by a man because –

(i) it is, or is part of, a hospital, prison or other establishment for persons requiring special care, supervision or attention, and

(ii) those persons are all men (disregarding any woman whose presence is exceptional), and

(iii) it is reasonable, having regard to the essential character of the establishment or that part, that the job should not be held by a woman.

[United Kingdom, Sex Discrimination Act of 1975]