Commons Speaker John Bercow has caused controversy by citing a 400-year-old rule which means Theresa May cannot  bring her EU Withdrawal Agreement back before MPs unless it is substantially different from the one which was decisively defeated last week.

Here we take a look at the Speaker’s powers:

– What is the role of the Speaker of the House of Commons?

The familiar shout of “Order, order!” explains part of the Speaker’s job in Parliament. They are in charge of keeping order during debates, and calling different MPs to take their turns speaking on various issues.

– What powers does the Speaker have?

The Speaker is the highest authority in the House of Commons and has the power to ensure MPs follow the rules, including asking them to be quiet while others are speaking, directing a member to withdraw remarks if they are deemed to be abusive, and suspending the sitting of the House if there is judged to be serious disorder. An MP can be suspended if they are felt to have been deliberately disobedient.

– Is the Speaker impartial?

The speaker is an elected MP, like all their colleagues in the House, and they are supposed to deal with constituency business as normal. However when elected they are required to resign from their political party and to keep themselves separate from political issues, remaining impartial.

– How is the Speaker elected?

The current speaker was elected in 2009, using an exhaustive secret ballot system. MPs marked an X next to the candidate of their choice on a list. John Bercow got 322 of the 593 ballots cast, at which point the question proposing the successful candidate as Speaker was put before the House and he took the chair.

– How has the current Speaker enforced the rules most recently?

Mr Bercow cited the Commons rulebook Erskine May – the authoritative book on parliamentary law and practice – as he set out a convention dating back to 1604 that a defeated motion cannot be brought back in the same form during the course of a parliamentary session.

His ruling, which came in an unexpected statement to the Commons on Monday, indicated that the Prime Minister cannot bring her EU Withdrawal Agreement back before MPs unless it is substantially different from the package which was decisively defeated last week.