How MPs vote

Less than forty-five minutes to go. 

The question remains over how many Labour MPs support the motion. Early estimates said 100 but that figure later came down to 40.

If the latter figure is nearer the mark it could be very close for Cameron.

The Commons uses a quaint, some say archaic, voting system for motions before the House.

MPs form queues and walk through either one of two corridors to show their support (the ayes), or opposition (the noes).

The counters then relay their tallies to the chair, who calls the vote. Politics.co.uk has a fuller explanation here.