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I hope that the escalators in the Sainsbury's in Darlington, where one is repeatedly urged to face the direction of travel (Letters, 23 August), ascend eastwards, or else the speed of the Earth's rotation, about 600mph in the latitude of Darlington, will massively outweigh any escalator speed (hopefully), so one would have to face backwards to comply with the instruction.

Of course, to comply fully, one must also account for the speed and direction of the Earth's orbit around the Sun, the Sun's orbit around the Galactic Centre, the motion of the Milky Way towards Andromeda, the expansion of the Universe, the...oh, never mind, I'll use the stairs.

Hillary J. Shaw, Senior lecturer, Department of food science and agri-food supply chain management, Harper Adams University College