I love this! A beautiful circle of history from Deep Time through an early medieval hall in the City of London and Gerard, its attendant giant, and back to the dinosaurs of in Crystal Palace!
Our tale starts in the swamps of the Bathonian Age  in the middle of the Jurassic Period, in the area that 167million years later will be Normandy. In warm seas and lagoons millions of beautiful feathery Sea Lilies filter the waters in lagoons and deposit lime mud pellets that will build up and be transformed over millions of years into limestone, while dinosaurs wander to and fro.  In the geologic timescale the Bathonian is a stage of the Middle Jurassic, taking its name from Bath, built also of a limestone from this time.
And the limestone of this place came to be called Caen Stone or more correctly, ” the Pierre de Caen … a bioclastic, crinoidal, pelletal, grainstone-packstone. The Crinoid animal (Sea Lily) feeds by filtering sea water and produces lime mud faecal pellets. Such pellets (<0.1mm) are common in many Jurassic & Early Cretaceous limestones and comprise most of the fabric of Caen stone. ” 
And the swamps and lagoons were alive with dinosaurs! “… the sea bed was populated by corals, belemnites, large nautiluses and giant ammonites. The banks of the lagoon were infested with crocodiles. Teleosaurus cadomensis was a gavial specific to the area recognizable from its thin snout about a metre long. Over 450 specimens of this species have been discovered in and around Caen, but sadly were destroyed in the bombing raids during the summer of 1944 which wiped out the university, where they were kept. … [ and note ] … the discovery of Megalosaurus’s, the latest of which being the one at Conteville (Calvados)” from Caen Stone – From the Dinosaurs to the Cathedrals 2010. 
Over the millions of years that followed the sea bed rose and was crushed and transformed into “The best-known finest quality stone used for ornamental work in English Cathedrals and Churches .. the Pierre de Caen which is the upper part of the Calcaire de Caen (Caen Limestone Formation). .. a cream-coloured fossiliferous Middle Jurassic limestone (contemporaneous with the Bath Stone of England), quarried above and below ground in the area around Caen in Normandy, NW France. From the 11th century, southern England was the main importer of Caen Stone and again in the 19th century.”  and  
And all those millions of years later the Normans after they had conquered England in 1066, brought their Norman stone with them, in London famously for the White Tower, now part of the Tower of London, but also for many other buildings including the crypt of the Hall of a Vintner (or Pepperer) and Lord Mayor of London John Gisor. Over time Gisor’s Hall became Gerard’s Hall – “This hall where Mr. Gisors, when Lord Major of London, used to transact the business of the city, is now made use of as a cellar to an inn, known by the name of Gerard’s Hall, in Basing Lane.” 
“On the south side of Basing Lane,” says Stow, “is one great house of old time, built upon arched vaults, and with arched gates of stone, brought from Caen, in Normandy. The same is now a common hostrey for receipt of travellers, commonly and corruptly called Gerrarde’s Hall, of a giant said to have dwelt there.” 
The inn was fronted by a large statute of Gerard “a quaint gigantic figure of seventeenth century workmanship.” that can now be seen in the Museum of London.
Sadly, the Gerard’s Hall and crypt were demolished in 1852 when Cannon Street was extended to St Pauls and Basing Street disappeared. It was proposed however that due to their antiquity, that the stones be re-erected at Guildhall, and they were numbered for that purpose on removal. 
Meanwhile: The massively successful Great Exhibition had been held in Hyde Park in 1851, with its enormous Crystal Palace brilliantly designed by gardener Joseph Paxton, visited by six million people!  So successful was the exhibition that a decision was taken to re-erect the vast palace on the slopes of Sydenham Hill in distant Penge in a massive new park of terraces lakes and fountains … and dinosaurs! 
And this being the Victorian age of discovery and science and a thirst for knowledge and understanding, Paxton created an exhibit of dinosaurs and geology in the southeast of the park by one of the new lakes. Using the knowledge of the “outstanding naturalist” Richard Owens  sculptor Benjamin Waterhouse Hawkins  was engaged to build 30+ ‘dinosaurs’ or palaeontological statues.
“Hawkins is mostly synonymous today with Crystal Palace and you might get the impression that designing and building life-sized prehistoric animals is all he ever did (his ill-fated involvement in an American prehistoric park is similarly famous). In fact, he was a highly accomplished and skilled artist of modern zoological subjects long prior to being commissioned for this job, famously illustrating, for example, some of Darwin’s works on the voyage of The Beagle” 
Next to the dinosaurs is a now sadly diminished geological exhibit, 5 walls of quarried and brought in stone in realistic strata and formations and unconformities to demonstrate current understanding of the new subject – “A vision of Deep Time” 
Of the 30+ dinosaurs Hawkins built 2 stand out as being from the Bathonian. the Perfect Lizard, Teleosaurus  and the Giant Lizard, Megalosaurus.  And as noted above both these creatures have been found in the fossil record in Caen stone in Normandy. [ Do you see where this is going?]
Hawkins built his dinosaurs on site using moulds taken from indoor clay models. He “ … set up a workshop on site at the park and built the models there. The dinosaurs were built full-size in clay, from which a mould was taken allowing cement sections to be cast. The larger sculptures are hollow with a brickwork interior.”  The large ones he built of brick and iron hoop construction with concrete and then cement facings. And he needed stone for the dinosaurs and the mounds they were to stand on. 
Meanwhile: After the Gerard’s Hall crypt had been demolished but numbered to be re-built, it became clear it was not going to Guildhall. But there was another solution.
Thomas Younghusband was a carter and inn keeper and carried out the contract to move the original Crystal Palace from Hyde Park to what was then Sydenham Hill in Penge. BUT coincidentally he was also the Inn Keeper of Gerard’s Hall! 
And so the plan was changed for the crypt to be rebuilt at Crystal Palace “ The stonework was then removed to the Crystal Palace to be there set up; but this design was never fulfilled, and the stones were used for other purposes.”  “… and the stones were used instead by Benjamin Waterhouse Hawkins to sculpt model dinosaurs for the “geological islands” in the park”. 
And so, at Crystal Palace Park stands a Bathonian Age Megalosaurus and Teleosaurus’s, standing on and full of Bathonian Age limestone and who knows, deep within their ‘flesh’ is some fossilised DNA of themselves, waiting for some unexpected and inexplicable quirk of to nature to somehow spark life and into living Giant and Perfect Lizards! Well one can only dream! 😀
p.s. hopefully I’ll get to Normandy next year to check out the quarries.
Sadly there’s nothing to see at the site of Gerard Hall but Gerard the giant is on a wall in the Museum of London in the City at the start of the Modern galleries.
Crystal Palace Park is well served by public transport with trains from London Victoria, London Bridge and Highbury and Islington/Dalston. The dinosaurs are only 5 minutes, right and right again, out of the station