D. L. Shell published in 1959, [4], a fast algorithm for internal sorting. R. M. Frank and R. B. Lazarus pointed out in 1960, [3], a disadvantage in the original design of the algorithm and changes were proposed based on heuristic arguments. J. Boothroyd took care of Frank and Lazarus objections in an elegant algorithm published 1963, [1]. If we change Boothroyds algorithm slightly we get an algorithm which, in the general case with the arguments of Frank and Lazarus, is even worse than the original one. On the other hand this algorithm has the advantage that it is easy to analyse theoretically. To the author's knowledge such an analysis has not yet been given for any of the other Shellsort algorithms.