Barney Is a Trainee Chef

True/False

Barney is a trainee chef. His contract requires him to be available 'from 5pm to 10pm and any other hours that may be required'. After working two 90 hour weeks in a row, he refuses to stay late on Monday and instead returns home to sleep. When his employer argues that he is in breach of contract, Barney argues that there is an implied term in law limiting working hours on health and safety grounds. Is Barney right?