What is the test for establishing that a risk is not an employment risk?

And at p. 68 ([1914] A.C): As I have already said, however, the question of within or without the sphere is not the only convenient test. There are others which are more directly useful to certain classes of circumstances. One of these has been frequently phrased interrogatively. Was the risk one reasonably incidental to the employment? And the question may be further amplified according as we consider what the workman must prove to show that a risk was an employment risk, or what the employer must prove to show it was not an employment risk. As regards the first branch, I think the point is very accurately expressed by the Master of the Rolls in the case of Craske v. Wigan, [1909] 2 K.B. 635, 78 L.J.K.B. 994, where he says: “It is not enough for the applicant to say the accident would not have happened if I had not been engaged in that employment or if I had not been in that particular place.’ He must go further and must say The accident arose because of something I was doing in the course o£ my employment or because I was exposed by the nature of my employment to some particular danger.’” As regards the second branch, a risk is not incidental to the employment when either it is not due to the nature of the employment or when it is an added peril due to the conduct of the servant himself.