If an individual is a director of a company and the company has no other employees, that individual is not a worker by virtue of any office that they hold or contract of employment under which they work. The company is therefore not subject to the employer duties in relation to that individual.
However, if the company takes on a second worker, and both the director and the new employee work under a contract of employment, then both the director and the new employee will be workers for the purposes of the employer duties and the company will have responsibilities in relation to both of them.