The only question remaining is; " What is the criterion as to
whether the occurrence was outside the sphere of employment ?"
No doubt where, as Lord Macnaghten said in Reed v. Great Western
Railway Co. (1), quoted by Lord Dunedin in Lancashire and
Yorkshire Railway Co. v. Highley Q), an employee is engaged on a
purpose of his own, and not in the execution of his duty or in the
interest of his employer, he puts himself "outside the area of
protection." But the circumstances of industry are so various that
great difficulty nearly always arises in determining whether the
employee at the crucial moment was acting within or beyond the
sphere of his employment. The test as a legal proposition is simple :
" Was he doing what he was employed to do, however improperly,
or was he doing something altogether outside his employment ?"
(See Garallan Coal Co. v. Anderson (3).) But as between employer
and employee the method of approaching that question is all-
important. In my opinion it depends on the way in which the
terms of the employment are conveyed, and the proper criterion is as
follows : How would the workman reasonably understand the terms
of or the instructions in his employment ? To determine this, the
ordinary process must be applied, thus : - (1) If those terms clearly,
either expressly or by implication, limit the area of the employment
as distinguished from merely regulating the workman's conduct
within that area, then, if in fact the workman at the crucial moment
was, in contravention of those terms, acting outside the area, the
employer is not liable. In other words, if no person in the workman's
situation, having regard to the terms of his contract of employment
or to his instructions, could reasonably believe that at the moment
of the accident he was in any way engaged in performing any of
his duties as employee, then he was acting outside the sphere of
his employment. (Garallan Co.'s Case (3); Wilsons and Clyde Coal
Co. v. M'Ferrin (4).) (2) But if the terms of his contract or his
instructions are, in relation to the employment, ambiguous to the
31, at p. 34, (3) (1926) 42 T.L.R. 747, at p. 748 ;