You would not give a second glance to a pair of unremarkable, slightly sunken flowerbeds in a Liverpool churchyard. In fact, they mark the location of burial pits where as many as 15,000 people were interred over a period of just 26 years.

The pits were cut into sandstone to a depth of two double-decker buses. The diggers kept two or three pits open at a time, putting 120 bodies into each pit before filling them in, possibly adding lime to speed up decomposition. After about seven years the remains were disinterred and placed in charnel pits – also dug into solid rock – in the church crypt.