It is the Church of St Martin with Ludgate and the Ludgate and Newgate Prisons were nearby. ZXZ
The gate was one of three separate sites that bore the name Ludgate Prison. In 1378 it was decided that Newgate Prison would be used for serious criminals, and Ludgate for Freemen of the City and clergy who were imprisoned for minor offences such as debt. By 1419 it became clear that prisoners were far too comfortable here, as they were more likely to want to stay than to pay their debts and leave. They were all transferred to Newgate prison for this reason, although that prison was so overcrowded and unhealthy that they soon returned.