A person is drunk within the meaning of this section if owing to the influence of alcohol or any drug, whether alone or in combination with any other circumstances, he is unfit to be entrusted with his duty or with any duty which he might F2reasonably expect to be called upon to perform, or behaves in a disorderly manner or in a manner likely to bring discredit on Her Majesty’s service.

Every person subject to this Act who is drunk, whether on duty or not, shall be liable to imprisonment for a term not exceeding two years or any less punishment authorised by this Act.