London Undone's City of London Churches series approaches each building the way a patient guide would, from the door inward and one detail at a time. Catherine Cartwright introduces each visit and asks the questions, but most of the knowledge comes from her companions. Kevin Larder, a city guide who is also a volunteer guide at St Bart's Hospital Museum, walks her through St Helen's Bishopsgate and St Bartholomew the Great. Signe, of the Friends of the City Churches, sits with her in St Mary Abchurch and St Margaret Lothbury. At St Mary-le-Bow the voice is the rector's, speaking from the crypt chapel after twenty years in post. Several conversations begin with the name. Nobody knows where Lothbury comes from, Abchurch may mean 'Up Church' for its place on the slope down to the Thames, and Mary-le-Bow's name is read as Norman French, pointing to a foundation soon after the Conquest. Then attention turns to what is actually in front of them. St Helen's Bishopsgate has two naves and two entrances, a parish church from 1140 beside a nuns' choir from 1210. St Margaret Lothbury owes some of its fittings to an incumbent named Ingram, who picked through other people's demolition sites, and its huge pulpit canopy came from All Hallows the Great. At St Mary Abchurch, letters from Grinling Gibbons asking to be paid turned up in the parish chest in the 1950s, preserved thanks to wardens from a merged parish who queried every penny. St Mary-le-Bow tells a different story. Its post-fire church, by Wren or possibly Hooke, sat on the old crypt as a preaching box modelled on the Temple of Maxentius in Rome, and after the destruction of 1941 almost nothing but the walls survived. The restorer Lawrence King rebuilt it with the aim of making it London's liturgical movement church. Saints are treated with affection. St Etheldreda is introduced as an Anglo-Saxon princess, twice married, who became abbess of a community at Ely, and the guest there, a lecturer, jokes about thinking of her before every talk, since she is claimed as patron of throat infections. Nearby glass shows St Brigid, recalling the Irish population in the area when the railways were being built. St Bartholomew the Great brings lighter asides, with film shoots from Shakespeare in Love to Thor: The Dark World, which used it as Valhalla, and reportedly the Muppets, alongside Norman fabric some 900 years old and a cloister door from 1400. Some visits end with practical pointers, such as ringing St Helen's ahead or checking events for St Bartholomew's 900th anniversary, and one carries a postscript about a Russian congregation that left St Mary Abchurch before its service could be recorded. What a listener gets is a habit of reading these churches as layered records, where a pulpit canopy, a memorial half under a radiator cover or a trace of the River Walbrook each holds a piece of the City's past.