A night watchman is employed to patrol a builder's yard overnight. He needs to provide his own clothing and this includes a warm waterproof jacket that he keeps at the yard and only wears at work. The jacket has a reflective surface so that he can be seen in the dark.
No deduction is due for the cost of the jacket or any of the
other clothing that the night watchman wears. The jacket is
ordinary clothing but of a type dictated by the nature of his job.
It provides him with warmth and cover and the cost is not incurred
wholly and exclusively in the performance of his duties, see