The standard toilet signs for men and women in the UK were designed by Margaret Calvert, a renowned graphic designer who played a pivotal role in shaping the visual identity of Britain in the mid-20th century. In 1963, Calvert was commissioned by Jock Kinneir, a fellow designer and close collaborator, to create a comprehensive signage system for the newly formed British Rail. This project, known as the Rail Alphabet, aimed to establish a unified and easily recognizable visual language for railway infrastructure and facilities.

Calvert's approach to designing the toilet signs was characterized by simplicity and clarity. She utilized bold outlines, minimal details, and a geometric style that aligned with the overall aesthetic of the Rail Alphabet. The male and female symbols were derived from a common base shape, ensuring a sense of visual harmony while maintaining distinct identities. The resulting design, with its clear and uncluttered forms, has become an enduring symbol of British design and remains widely used in public spaces throughout the UK.

Calvert's contributions to the Rail Alphabet and her work on the toilet signs exemplify her dedication to creating functional and aesthetically pleasing design solutions. Her work has had a profound impact on the visual landscape of Britain, and her legacy continues to inspire designers and influence public signage systems worldwide.