Now or never? Tory MPs face last chance to ditch Johnson before election

For weeks now, Westminster has been fixated on the number 54 – the tally of Conservative MPs needed to trigger a vote of no confidence in Boris Johnson. If, as now appears increasingly likely, that threshold is breached in the coming days, another number will become all-important: the 180 MPs required to kick him out of Downing Street.

The Tories have a reputation for ruthlessness when it comes to throwing out their leaders, and the rules of…