The Chapel of St Stephen's has shaped much of the nature of the House of Commons as we know it today. In 1348, Edward III established the Chapel as a college for secular canons.
When services were conducted, the choir sat in stalls facing each other across the aisle. At the west end of the chapel they built a great screen, with double doors at its centre.
In 1547, Edward VI granted the Commons the use of the Chapel after the dissolution of St Stephen's College. When the MPs moved in, they found the arrangement of choir stalls for the choir and a screen near one end of the Chapel still in place.
Commons take over Chapel
So they simply took over both stalls and screen for their purposes; they sat in the choir stalls and made speeches to each other across the aisle of the Chapel.
This configuration may have in fact encouraged the development of the two-party system, of government versus opposition, in British political life. If the Commons had continued to sit in the octagonal Chapel House, the political history of Britain might have been very different.
How they voted
The MPs also made ingenious use of the screen which the canons left behind; those who voted in favour of a motion would walk through its right-hand door, while those who did not would exit through the left door. Today, MPs voting aye continue to file out to the lobby on the right, and those voting no, to the lobby on the left.
However, the MPs could not quite forget that their home was once a chapel. The altar with its crucifix was still there, and they would bow towards it every time they went in or out of their Chamber. To this day, MPs still bow towards the end of their Chamber as they exit or enter.
The first Speaker's Chair was placed on the altar steps of St Stephen's Chapel, where he could see and be seen. Today, the Speaker of the Commons still climbs steps to get into his Chair.