St Mary-at-Hill is an Anglican parish church in the Ward of Billingsgate, City of London. It is situated on Lovat Lane, a cobbled street off Eastcheap. It was founded in the 12th century as “St. Mary de Hull” or “St. Mary de la Hulle”. It was severely damaged in the Great Fire of London in 1666. Wikipedia
I have found this a difficult church to visit, but I may have just been unlucky. To date it has not been part of London Open House.
Opening Times: Mon-Fri: 10am-4pm
Friends’ Watchers keep it open on Thursdays.
Nearest tube: Monument