The most exciting event so far on the London end of the Building London blog, as opposed to standing in, rowing across or gazing out of vast quarries in Devon, Cornwall, the Midlands or Wales, has been my, er, discovery of the Guildhall crypts! I had asked for, and received permission, to inspect and photograph the ancient walls of the Guildhall of the City of London, and on the way out, noticed some stairs down, and asking permission of the security guard, I went down and came into the magical Guildhall Crypts! It’s embarrassing in a way as my research was at that point fixated on medieval walls, of which Guildhall stands out in London, that I must have missed the existence of these incredible crypts! There is almost nothing else like them in all of London and even the rest of Britain. Maybe bits of the Palace of Westminster and Westminster Abbey, but whatever, they are stunning. And I was privileged to be able to see them empty and serene!
The Guildhall, as the political centre of the City of London is both one of the most important buildings in both the old City of London and the ‘new’ wider London and one of the oldest and under it are these two ancient crypts or an ‘undercroft’. The current Guildhall, there seem to have been ones before this one, is thought built between 1411 and 1440. And although it had to be restored after damage from the Great Fire of 1666, was restored again in 1866 and again the 1940s after being burnt out in the Blitz, the walls, and crypts remain fundamentally the same. 
Historic England’s listing states “Early C15, much restored. … The building is of squared rubble with ashlar dressings and inner facing. The eastern half of the undercroft is original with clustered columns and ribbed vault. The western half was rebuilt in brick in the late C17.” 
But as with so many old buildings there is disagreement re the age of the crypts with modern research showing the West Crypt is much older.
Pevsner states that the 15thC Guildhall was the 3rd Guildhall which would makes sense that the crypts could be older “Built by the master mason John Croxton or Croxtone from 1411 to c.1429 … It is known to have been at least the third Guildhall on the site …” 
Walter Thornbury in his ‘Guildhall’, in Old and New London: Volume 1 (London, 1878) (reproduced in British History Online) stated the East Crypt dated from the 1411 building
“This crypt is by far the finest and most extensive undercroft remaining in London, and is a true portion of the ancient hall (erected in 1411) which escaped the Great Fire of 1666. It extends half the length beneath the Guildhall, from east to west, and is divided nearly equally by a wall, having an ancient pointed door. The crypt is divided into aisles by clustered columns, from which spring the stone-ribbed groins of the vaulting, composed partly of chalk and stone, the principal intersections being covered with carved bosses of flowers, heads, and shields. The north and south aisles had formerly mullioned windows, long walled up. At the eastern end is a fine Early English arched entrance, in fair preservation; and in the southeastern angle is an octangular recess, which formerly was ceiled by an elegantly groined roof, height thirteen feet. The vaulting, with four centred arches, is very striking, and is probably some of the earliest of the sort, which seems peculiar to this country. … In 1851 the stone-work was rubbed down and cleaned, and the clustered shafts and capitals were repaired;” 
As did Charles Dickens, no less, who in 1879 also went with the 1411 date: “Guildhall dates originally from the time of Henry IV., which, however, is not responsible for the mean and miserable jumble of a front stuck on to it by Dance in 1789. The old walls, on the other hand, are of so splendid a solidity that they stood triumphant through the Great Fire of 1666, towering amid the flames “in a bright shining coat, as if it had been a palace of gold or a great building of burnished brass.” The old crypt, too, of the same date (1411), is a beautiful piece of work, 75 ft. long by 45 ft. wide, and divided into three aisles by six clusters of circular columns in Purbeck marble, supporting a fine groined roof, partly in stone, partly in chalk and bricks; the principal intersections being covered with carved bosses of heads, shields, and flowers. The vaulting, with four-centred arches, is considered to be one of the earliest as well as one of the finest examples of its kind in England.” 
Guildhall , 1042, the Guildhall events page , Exploring London  and Know Your London  all suggest the East Crypt dates back to the 11thC but these dates are now regarded as inaccurate.
It is now generally agreed that the West Crypt is late 13th or early 14thC while the East Crypt dates to the 15thC building as stated by Graham Glass and Stephen Dinsdale in their ‘Guildhall – City of London History Guide Companion’ from 2018: “Beneath the Great Hall lies the undercroft, split into two ancient crypts. The East Crypt and the West Crypt together correspond to the footprint of the Great Hall above them. It was believed for many years that the East Crypt was older but we now know that the West Crypt is the older of the two.
As far back as anyone could remember, the West Crypt had just been used for storing records and other materials. Following it’s restoration in 1972 we now know why it was thought to be newer. Much of the West Crypt had been barrel vaulted with bricks since being damaged during the Great Fire of 1666. Until the brickwork had been removed, exposing the original stone work, it wasn’t possible to assess the crypt properly. It’s now thought the West Crypt dates to the late thirteenth or early fourteenth centuries and this makes it significantly older than the Great Hall
The stonework of the West Crypt is quite plain, stands eleven feet high and is five bays long. The octagonal piers are undecorated, have no capitals and rise directly into the vaults. There is speculation that it may once have been ‘L’ ‘ shaped and may even have been the floor of an earlier Guildhall.. The new stonework reflects the old. The paving is of York Stone with Doulton and Portland stone being used in the repair of the columns.
The East Crypt by comparison is well studied , though some mystery still remains. Built by John Croxtone, it is slightly higher at thirteen feet and too finely decorated to be use solely for storage. It is hour bays long and like the West Crypt has clustered pillars. These pillars are shiny Purbeck Marble shafts, Mansfield stone capitals and Godstone sandstone bases.” 
Ditto John Scofield in his Building of London states “ The Guildhall has stood on part of its present site from a least the late thirteenth century and possibly from the second quarter if the twelfth. It is likely that about 1270-90 the rising fortunes of the city promoted the building of a new guildhall, probably with aisles, on a stone undercroft which survives in part as the western crypt of the present Guildhall. In 1411 .. John Croxtin was engaged .. to build a replacement … [ choosing ] to incorporate most of the old undercroft and extend the building providing it with an eastern undercroft” 
And the excellent London Encyclopaedia states they are 13thC or earlier – “Beneath the hall was a large crypt which survives today, the most extensive mediaeval crypt in London. It is in two parts, the western crypt probably dating from the late 13thC or earlier.” 
I imagine the above have used the two key references to date the crypts which are Peter Marsden in his ‘The pre-1411 Guildhall of London’ and Caroline Barron’s “The Medieval Guildhall of London” 1974.
Marsden notes that excavations have shown evidence of a building from 1127 and argues that “it is possible that the west and south walls of the crypt may have belonged to this first building” but I’ve not seen anyone provide any certainly to this and he then notes that Barron “tentatively suggests that the vaulting may have been constructed during the late 13thC”. 
A MOLAS ( Museum of London Archaeology ) report from 2007 states “.. archaeological evidence has corroborated Barron’s convincing argument that the west crypt of the surviving Guildhall dates to c 1300” and notes that “In her 1974 publication The Medieval Guildhall of London, Caroline Barron demonstrated that the surviving west crypt of the 15th- century Guildhall must have been part of an earlier building, skilfully incorporated in the new hall by the master mason John Croxtone…. Barron used architectural and documentary evidence to conclude that the west crypt was part of the undercroft of a late 13th-century Guildhall. Combining Barron’s work with the results of the excavation of the adjoining Guildhall chapel (B220, Fig 138), it can be suggested that the two buildings were erected in a single construction programme as part of an ambitious development scheme beginning in 1298 and continuing in the first half of the 14th century.”  
Whatever the dates of the crypts and whenever they have been restored, they are absolutely gorgeous! :-O :-O
But what are they built from and where is that from!
Of course the focus of the Building London blog is not so much about dating things as what they are made from, though the two things are linked. And the crypts have 4 components: the walls, the vaulted ceilings, the pillars and the floor and they are all made from different stones.
J.W. Bloe’s in his Building Materials in Early and Mediæval London (1930) notes the 3 main stones used in the crypts: Purbeck Stone, “The pillars of the Guildhall Crypt (15th-century) are remarkably well preserved.”,
Kentish Stone and Ragstone, “this stone was almost universally used for the bodies of the walls of churches and other important buildings, such as … the Guildhall” and Caen Stone, “the vaulting of the Crypt at the Guildhall”. 
Alderman James Baddeley in the 1951 edition of ‘The Guildhall of the City of London’ states that “the [pillar] shafts are of blue Purbeck Marble, the caps are yellow Mansfield stone, bases and the vaulting ribs are sandstone from Godstone, usually known as freestone, and are filled with chalk.” This is interesting as he suggests that what others call Reigate is specifically from Godstone and I wonder if that is from records. He does though wrongly state that the crypts both date from Croxton. 
The Building London Blog has looked at Kentish Ragstone on a few occasions, https://buildinglondon.blog/2021/12/26/24-kentish-ragstone-an-introduction-to-the-most-important-historical-stone-in-london/, Chalk once https://buildinglondon.blog/2021/08/26/14-totternhoe-stone-a-chalk-you-can-build-with/, and Caen Stone once before [ https://buildinglondon.blog/2021/11/26/19-a-jurassic-tale-of-a-giants-crypt-in-the-city-of-london-and-the-crystal-palace-dinosaurs/ ] but not Purbeck Marble. And there will be a proper site visit/report back to Purbeck this year.
In terms of chalk Thornbury and Dickens above and John Timbs in 1855 have all stated that the vaulting was “.. composed partly of chalk and bricks”, though there’s no clear indication where it is from. 
Re the Reigate or Godstone stone, Dimes notes that it was used in “the vaulting of the crypt of Guildhall” 
And re Kentish Ragstone see this from London Pavement Geology. “The original 15th Century walls of the Guildhall are built from carefully squared blocks of Kentish Ragstone.” 
and there are several references inc above to Caen being used for the ribs of the vaults including Blow above 
And while the walls and the vaulting are indeed stunningly beautiful it’s the Purbeck Marble that is the jewel in the crown! (Nb It’s unclear to when the current pillars date and the MOLAS report suggests they may be from 1851.)
Purbeck Marble is an exceptionally beautiful stone when polished but it’s not a marble. It’s called a marble as it polishes up like a marble. But in fact it’s “… a fossiliferous limestone found in the Isle of Purbeck, a peninsula in south-east Dorset, England. It is a variety of Purbeck stone that has been quarried since at least Roman times as a decorative building stone….Purbeck Marble is not a metamorphic rock, like a true marble, but is so-called because it can take a fine polish. Its characteristic appearance comes from densely packed shells of the freshwater snail Viviparus.” 
It is found in or from “The Purbeck Group, which is now believed to be largely of early Cretaceous age … a series of thin limestones, mudstones and calcareous clays deposited in shallow freshwater or marginal marine environments. The limestones have abundant fossils, mostly bivalves, but the beds worked as ‘marbles’, which are higher in the sequence, contain mostly gastropods.” 
Even though coming from a very small area it became a very important and widely used stone and so important as to have become Crown property.
“Purbeck marble was used to adorn the interior of many religious houses like those at Lincoln, Chichester, York, Wells and Winchester. Salisbury Cathedral developed between 1220 and 1258 in the Early English style using much Purbeck. At the same time Purbeck Stone was used in the actual building of the churches. Indeed in the thirteenth century the rebuilding of Westminster Abbey was a huge advance for many local marblers who went on to establish themselves in a London stone trade. Legg comments that their “jobs in London were a mark of complete royal acceptance; it gave Purbeck industry a place inside the closed-shop of building trades”. (Legg, 1989). An extension of this royal acceptance can be assumed from the fact that the earliest royal effigy in England, of King John at Worcester, was carved in Purbeck Marble.
Of course the importance of the marble industry to the crown was twofold. Yes they appreciated the beauty of the material and its absolute suitability to the purposes set out above, but apart from this the stone was ‘crown property’ and its profits could only benefit the monarchy. Some have attributed the increase in use during the thirteenth century to this factor; the Purbeck Quarries provided revenue to the royal purse. Furthermore Henry III was renowned for his eagerness to build. (G. Drury, 1948).” 
With Guildhall one of the most important buildings in the London you can see why the City Aldermen would have wanted to use this stone or maybe they just got some surplus from Westminster Abbey!
It should be noted that another Purbeck stone, also a limestone but one that doesn’t polish to a ‘marble’, and that was much used for paving, simply called Purbeck Stone was also used for paving the main hall above “In 1422 the executors of Whittington, one of whom, John Carpenter, was the compiler of the famous Liber Albus, gave twenty pounds towards the paving of the Hall with Purbeck stone…” 
The History Girls blog note that Purbeck had an transport advantage as being on the sea, which in the Medieval period was an easier way of transport often than across land. “Purbeck was successful in part because of the coastal location of the resource, which made transportation easy. In 1175, columns were shipped from Corfe to Durham Cathedral. Capitals and bases went to Norwich, to Westminster, to Vale Royal. In 1375 a ship called the Margarite out of Wareham was listed as transporting cargoes of Purbeck to London… In 1386 the same ship transported Purbeck from Dorset to London for the tomb of Edward III…”. And they also note that in the period Caroline Barron sees the, what would become, West Crypt being built, Corfe marble workers settled in London … “The London craftsmen of Purbeck originally came from Corfe but settled in their own community in the capital. The biggest influx of craftsmen seem to have arrived during Henry III’s drive to build and beautify Westminster Abbey from 1245. By 1253 there were 49 marblers at work on the site, all cutting and polishing the Purbeck blocks and shafts.” 
If you’ve not see Purbeck Marble up close it looks like this and check this link. https://www.virtualmicroscope.org/content/limestone-purbeck-marble-2 And this https://purbeckstone.co.uk/our-stone/purbeck-blue-marble/
In Guildhall the marble is generally in good condition but there is a suggestion that the current pillars are from 1851 and that would have been due to decay. Conservating it is a specialist craft. 
And big thanks to Charlotte Hedge at Guildhall for arranging access!
How to get there
Guildhall is very easy to get to being within short walking distance of a number of Moorgate, Bank and St Paul’s tube stations and bus routes in The City. You have to book tours to visit though. While you are there don’t miss the 2ndCRoman Amphitheatre, re-discovered in 1988, in the basement of the Guildhall Museum! 
 Charles Dickens (Jr.), Dickens’s Dictionary of London, 1879 https://www.victorianlondon.org/buildings/guildhall.htm
 Isca Howell, David Bowsher, Tony Dyson, Nick Holder https://www.mola.org.uk/london-guildhall-archaeological-history-neighbourhood-early-medieval-modern-times
 ‘Concluding survey of the County of London’, in An Inventory of the Historical Monuments in London, Volume 5, East London (London, 1930) British History Online https://www.british-history.ac.uk/rchme/london/vol5/xxiv-xlviii#h3-0004
 The Guildhall of the City of London 8th Edition 1951 Corporation of London
 Curiosities of London: Exhibiting the Most Rare and Remarkable Objects of Interest in the Metropolis. https://www.google.co.uk/books/edition/Curiosities_of_London/M5MLAAAAYAAJ
 London Pictures – Drawn with pen and pencil by The Rev. Richard Lovett M.A.