Even more complicated is a case with a passed pawn on the rook’s file; the win is possible only if the passed pawn is still on its initial position. A very instructive example illustrating this point is a study by H. Walker, published in 1841. White to move wins. His task is made more difficult by the fact that his king in contrast to the previous position, lacks manoeuvring space on the “outer” side of the passed pawn. Since no progress is possible along the a-file, White’s only chance is to penetrate across the “right” flank. However, whilst attempting the attack via d5-square White will need a ready answer to Black’s counter-attack with Kb4 forcing a drawn outcome.