For the purposes of this Part—
"work" means work as an employee or as a self-employed person;
an employee is at work throughout the time when he is in the course of his employment, but not otherwise;
a person holding the office of constable is at work throughout the time when he is on duty, but not otherwise; and
a self-employed person is at work throughout such time as he devotes to work as a self-employed person;
and, subject to the following subsection, the expressions "work" and "at work", in whatever context, shall be construed accordingly.
Regulations made under this subsection may—
extend the meaning of "work" and "at work" for the purposes of this Part; and
in that connection provide for any of the relevant statutory provisions to have effect subject to such adaptations as may be specified in the regulations.
The power to make regulations under subsection (2) above shall be exercisable by the Secretary of State . . ..