MPs will learn later which of them will lose their seats in constituency boundary changes - introduced to reduce the membership of the House of Commons by 50 before the next election.
The Boundary Commissions for England and Northern Ireland will release their redrawn political maps to MPs and journalists at mid-day on Monday, before making their proposals available to the wider public at midnight.
Whether MPs are able to keep their powder dry for those twelve hours remains to be seen, given that boundary changes have dominated the gossip and speculation at Westminster for the past week.
Scotland's boundary changes - likely to be just as controversial - will be announced in a few weeks, while changes in Wales have been delayed until the new year following embarrassing resignations at the Welsh Boundary Commission.
Speculation has been rife at Westminster that the changes - a Tory plank of the coalition agreement - could lead to some high-profile MPs losing their seats, possibly leading to squabbles between MPs over who should claim seats which have been merged.
Plans to reduce the number of MPs by 50 formed part of the Conservative manifesto at the last election. The Tories were also the architects of the plan to make the number of electors in each seat more even - addressing what many Conservatives see as an unfair bias towards Labour in the current system. Over time the number of voters in each seat has become uneven, particularly since populations in northern areas haven't risen anything like as fast as the south east.
Today's announcements are the results of the Boundary Commissions of the United Kingdom trying to re-draw constituencies to reflect these coalition policies.
Reports have suggested that high-profile MPs including Ed Balls, George Osborne and Charles Kennedy could find themselves without a seat under the changes.
A senior Tory close to the review process has played down claims that George Osborne's seat of Tatton would be affected - believing instead that another Tory seat in Cheshire would be the one to go.
The Shadow Chancellor Ed Balls is considered vulnerable, and could have to fight with Hillary Benn for a merged seat in West Yorkshire.