While operating a power driven grinding machine Mr Frost's thumb got through a small gap between the guard and the grinding wheel. He claimed compensation for his injury, alleging breach of statutory duty.
The house of Lords unanimously ruled that there had been a breach of statutory duty. The requirement that dangerous parts of machinery should be securely fenced was absolute.
It was not subject to derogation or dilution by such words as 'as far as reasonably practicable'.
The duty was to provide fencing which absolutely prevented any part of any person working on the premises from coming into contact with any dangerous part of the machine.
If the effect of this was to make the machine unusable then so be it.
Lord Morton thought that fencing should prevent an employee's clothing from coming into contact with dangerous parts of a machine.
The standard of fencing must be good enough to keep out the careless or inattentive worker as well as the meticulous, careful one.
