The Chapter House in the East Cloister was a meeting place where the monks gathered with the abbot to ‘hold chapter’: to pray, read from the rule of St Benedict, discuss the day’s business and when the abbot decided on punishments.
It was probably begun in 1246 and completed around 1255 as part of Henry III's re-building of the Abbey and is one of the largest of its kind (internally 18 metres or 60 feet). It is octagonal in shape with tiered seating for up to eighty monks and an imposing central pillar, fanning out to a vaulted ceiling. Henry of Reyns was the supervising master mason, probably with Master Aubrey.
Wall paintings still remain in many of the arches and depict scenes from the Apocalypse in the Book of Revelation. The Last Judgement, dating from about 1390, is shown on the east wall. Large figures of the Annunciation (the Virgin Mary and Archangel Gabriel) stand inside above the doorway. Around this doorway are small seated figures representing a 'Tree of Jesse'. The floor has one of the finest medieval tile pavements in England. it includes a Latin inscription translated as "As the rose is the flower of flowers, so is this the house of houses".
The Chapter House was also the place where the King's Great Council assembled in 1257. This was effectively the beginning of the English Parliament. Later on the House of Commons met here for a few years in the 14th century before using the Abbey Refectory for meetings. After the monks left in 1540 it was used until 1863 as a repository for State records.
The room was rescued and restored by the Abbey's Surveyor Sir George Gilbert Scott Between 1866-1872 he reconstructed the stone vault and roof and re-instated and re-glazed the windows. Much of this stained glass was damaged during air raids in the Second World War but some was salvaged and re-used in the post war glazing scheme. An inscription underneath the windows recalls the work of the original masons "In the handiwork of their craft is their prayer".
In the covered entrance to the Chapter House you can see what is claimed to be the oldest door in Britain, believed to date back to the 1050s.
Chapter House and Pyx Chamber Guide
Westminster Abbey Chapter House, the history, art and architecture... edited by W. Rodwell and R. Mortimer, 2010
From Painted Chamber to St Stephen's chapel: the meeting places of the House of Commons at Westminster until 1603 by Alasdair Hawkyard, Parliamentary History xxi, 2002.