I’ve heard people using back-to-back housing to mean terraces separated by back yards. But strictly, back-to-back houses are built against a party wall and face opposite ways. Byelaws after the passing of the Public Health Act 1875 prevented their continued construction.

In Birmingham, four of the city’s former thousands of back-to-backs are preserved by the National Trust off Hurst Street, which runs through the middle of what this year was officially designated Chinatown.