Housed now in the building it depicts, the Great Model of St Paul’s Cathedral was created by architect Sir Christopher Wren to show King Charles II what his proposed grand new English Baroque cathedral would look like (following the destruction of the medieval cathedral in the Great Fire of 1666).

Made of oak, plaster and lime wood, the model was made by William Cleere to Wren’s design in between September, 1673, and October, 1674, at a scale of 1:25. It measures 6.27 metres long, 3.68 metres wide and more than four metres tall, making it one of the largest in the UK.

The model, which cost about £600 to make – an extraordinary sum which could apparently buy a good London house, was designed to be “walked through” at eye level and, as well as being a useful way to show the King what the proposed building would look like, was also something of an insurance policy in case something happened to Wren.

It was based on drawings made by Wren and his assistant Edward Woodroofe on a large table in the cathedral’s convocation or chapter house (later demolished in the early 1690s) and was originally painted white to represent Portland stone with a blue-grey dome and gilded details.

There are some differences between the model and the finished cathedral – among them was a substantial extension of the quire, double-height portico on the west front, and, of course, the bell towers on the west front which were made in place of the cupola which was located halfway down the nave on the model.

Part of an earlier wooden model from 1671 also survives – it was apparently lost for many years and rediscovered in 1935.

The Great Model can be seen on tours of the Triforium.

WHERE: St Paul’s Cathedral (nearest Tube stations are St Paul’s, Mansion House and Blackfriars); WHEN: 8.30am to 4.30pm Monday to Saturday; COST: £21 adults/£18.50 concessions/£9 children/£36 family (these are walk-up rates – online advanced and group rates are discounted); WEBSITE: www.stpauls.co.uk (for tours, head to www.stpauls.co.uk/visits/visits/guided-tours)