In Anderson v. Mt. Clemens Pottery Company, 328 U.S. 680, 66 S.Ct. 1187, 90 L.Ed. 1515 (1946), the famous case that launched the Portal-to-Portal legislation, the Supreme Court found: Since the statutory workweek includes all time during which an employee is necessarily required to be on the employer's premises, on duty or at a prescribed workplace, the time spent in these activities must be accorded appropriate compensation. . . . . The time necessarily spent by the employees in walking to work on the employer's premises, following the punching of the time clocks, was working time within the scope of Sec. 7(a). . . . Such time was under the complete control of the employer, being dependent solely upon the physical arrangements which the employer made in the factory. Those arrangements in this case compelled the employees to spend an estimated 2 to 12 minutes daily, if not more, in walking on the premises. Without such walking on the part of the employees, the productive aims of the employer could not have been achieved. The employees' convenience and necessity, moreover, bore no relation whatever to this walking time; they walked on the employer's premises only because they were compelled to do so by the necessities of the employer's business. In that respect the walking time differed vitally from the time spent in traveling from workers' homes to the factory. . . . It follows that the time spent in walking to work on the employer's premises, after the time clocks were punched, involved "physical or mental exertion (whether burdensome or not) controlled or required by the employer and pursued necessarily and primarily for the benefit of the employer and his business." . . . Work of that character must be included in the statutory workweek and compensated accordingly, regardless of contrary custom or contract. (328 U.S. at 690-692, 66 S.Ct. at 1194.)