Contrary to the company’s (D) orders and law, a miner, X, asked P “shall we do” an illegal and dangerous explosives test, to which P relied “yes”. They were injured and P sued D for its employee’s negligence. HL held that where two fellow-servants combined to disobey an order deliberately though they knew the risk involved, volenti non fit injuria was a complete defence if the employer was not himself at fault and was only liable vicariously for the acts of the fellow servant. The statutory regulations did not change this.
Lord Reid: There is a difference between where P and D deliberately conspire to take an action despite knowing the risk involved and a case where P and D collaborate carelessly causing harm to one of them. In the first case (deliberate) Violenti non fit iniuria is a full defence and in the second (carelessness) contributory negligence is a partial defence. If P “invited or freely aided and abetted his fellow-servant's disobedience,” then he was “volens” and the defence applies.