Luxulyan granite, from near St Austell also plays a prominent role in building London.
Ussher et al. (1909) report that “The granite of St Austell has been used in public buildings in Oxford, London and Rome. London Bridge [the one now at Lake Tavasu, Arizona], the British Museum, and Crystal Palace were constructed partly of granite raised from the quarries of the eastern part of the St Austell Granite mass…”  Bristow quotes Keast (1982) stating that “Many famous buildings (e.g. the British Museum) and engineering structures (e.g. the old London Bridge) were constructed from it.”  Stanier (1999) says ” .. the following constructions which were made of ‘Luxulyan’ or Colcerrow granite: London …docks; the Crystal Palace(Sydenham); and the Caledonian Market (London). ” 
Colin Bristow states “ In the 1830s the great Victorian entrepreneur Joseph Treffry developed extensive quarrying operations in the Luxulyan valley (Keast 1982). Initially the granite was quarried to supply stone for major building works such as … the railway viaduct/aqueduct across the Luxulyan valley .. . Subsequently Treffry developed Carbean (SX063/577) and Colcerrow (SX065/579) quarries and established a large facility for producing dressed stone at Par, where he built a harbour to export china clay, ore and granite. This was connected to the quarries by a waterwheel powered 800 m long ‘Carmears Incline’ which conveyed the granite down to the level of Pont’s Mill, from where barges conveyed the stone in a canal to the works at Par, later converted to a railway..” 
Watson notes that the porphyritic large felspar granite of the Colcerrow quarries near St Austell, Cornwall “are called Horses Teeth as they by the quarrymen.” 
Sadly I didn’t manage to get into the massive Tregarden quarry which while abandoned and now a massive lake is very securely fenced off and the smaller Carbean, Colcerrow and Orchard quarries have been eaten up by the Cornish woodlands and off the beaten path.
But there is much to see in the Luxulyan valley. There is significant remnants of the inclines, leets and watered powered tramways and the extraordinary Treffrey viaduct that had a tramway above a aqueduct.
 “The geology of the country around Bodmin and St. Austell” Ussher et al. (1909) https://archive.org/stream/cu31924004731430/cu31924004731430_djvu.txt
 Bristow quotes Keast from from his “The King of Mid-Cornwall the life of Joseph Thomas Treffry (1782-1850) https://www.geolsoc.org.uk/~/media/Files/GSL/shared/Sup_pubs/2013/18675_file.rtf
 The Geology of the building and decorative stones of Cornwall – Supplementary publication – Granites and Elvans – Colin Bristow https://www.geolsoc.org.uk/~/media/Files/GSL/shared/Sup_pubs/2013/18675_file.rtf
 Watson British and Foreign Building Stones https://archive.org/details/britishforeignbu00watsrich/