Medieval Westminster was dominated by three buildings:
Westminster Abbey, Westminster Hall, and the 
magnificent Chapel of St Stephen's - begun by Edward I 
in 1292. The most superb Gothic building in the 
country, St Stephen's functioned as the monarch's 
private chapel until a fire at Westminster in 1512 led to 
Henry VIII changing his residence to Whitehall Palace. 
For a few years, it continued to be occupied by the religious 
order which had held services for the royal family - but these 
were dismissed in 1547 by Edward VI, and the chapel was handed 
over to the Commons.

In taking over, the Commons adopted the seating arrangements used by the clerics - two rows of stalls facing each other - and thus inadvertently laid the foundations of the British two-party political system.