The double border runs ninety metres from the Orangery to the Long Walk. By late June the back rows are above head height and the gravel path between them feels like a corridor.
It is planned every January on graph paper, at one square to a foot, by the same gardener who has looked after it for eleven years. About a third is changed each year.
Blue at the front, then purple, then the tall yellows at the back. That rule has not changed since 1920.