The Gatehouses and Beyond

The Middle Tower

Entering the Tower of London through the Middle Tower, the bulk of the stone seen is white Portland limestone from Dorset, which was used to reface and heighten the late 13th century tower in 1717; however, patches of unrestored ashlar stone can still be seen at lower levels and I am guessing that this is an example of Reigate stone, another Cretaceous glauconitic sandstone - this time mined from the Upper Greensand around the towns of Reigate and Merstham.

The geology around Reigate and Merstham

Like Kentish ragstone, I have never had an opportunity to investigate the geology around the North Downs or survey any of the ancient monuments or historic buildings associated with this building stone, such as Westminster Abbey and Hampton Court.  Although widely used in many of the royal palaces and other important mediaeval buildings for centuries, once Sir Christopher Wren established Portland limestone as London's principal building stone - after the Great Fire of London in 1666 - its use rapidly declined.

A view of the curtain wall at the Tower of London

At the Byward Tower, the white Portland limestone used in its restoration is obvious, but I couldn't positively identify the other stones. Compared to the grey/green colour of the Kentish ragstone seen in the curtain wall, the pale colour and squared form of the stone used to build much of this gatehouse indicates that it could also be Reigate stone.

The Byward Tower

Looking at the general colour and texture of its front elevation, the top left section is distinctly different to the Portland limestone and there are other variations that suggest that other  building stones may also have been used here. Quarr, Beer and Clunch are a few names of stones from southern England that respected authorities have identified in the mediaeval buildings of London, but I have no practical knowledge of any of them.

The church of All Hallows by the Tower

Before visiting the Tower of London, I had quickly explored the church of All Hallows by the Tower, where I had seen a distinctly green sandstone that I assumed to be Reigate stone, along with another glauconite bearing stone of quite different colour alongside it.

An extremely weathered block of stone

With this in mind, I soon encountered more examples of green glauconitic and calcareous sandstone that have been used for various phases of construction, restoration and repair - together with other stones that looked more like varieties of "Bath stone", a Jurassic oolitic limestone that was extensively brought into London with the development of the canals.