"Where the application of any provision of these Regulations is excluded by regulation 21… and a worker is accordingly required by his employer to work during a period which would otherwise be a rest period or rest break- (a) his employer shall wherever possible allow him to take an equivalent period of compensatory rest, and (b) in exceptional cases in which it is not possible, for objective reasons, to grant such a period of rest, his employer shall afford him such protection as may be appropriate in order to safeguard the worker's health and safety."
"(2). A mobile worker, to whom paragraph 1 applies is entitled to adequate rest, except where the worker's activities are affected by any of the matters referred to in regulation 21(e) [not material]. (3). For the purposes of this regulation "adequate rest" means that a worker has regular rest periods, the duration of which are expressed in units of time and which are sufficiently long and continuous to ensure that, as a result of fatigue or other irregular working patterns, he does not cause injury to himself, to fellow workers or to others, and that he does not damage his health, either in the short term or in the longer term."