Sch 10 para 11
(1) This paragraph applies if regulations under this Part create an offence consisting of— (a) a failure to comply with a duty or requirement to do something so far as practicable (or reasonably practicable), or (b) a failure to use the best means do something. (2) The regulations may provide that it is for the defendant to prove that— (a) it was not practicable (or reasonably practicable) to do more than was in fact done to satisfy the duty or requirement, or (b) there was no better practicable means than was in fact used to satisfy the duty or requirement.