Temple Church was built by the Knights Templar in the twelfth century. It is in the Inns of court near the River Thames in London and it's survived many changes, one of the most dramatic being a terrible bombing in the blitz. There's an unusual circular nave, which is where you can find the knights' effigies. One of them belongs to William Marshal, which made me think of Elizabeth Chadwick and her wonderful novel, The Greatest Knight.
Temple Church isn't always open to visitors so you have to pick your time for a visit. You can find out more about Temple Church, including opening times here: http://www.templechurch.com/