Election 2017: Parliamentary timeline

And that is how you spring a surprise.

Westminster's conventional wisdom had pretty much ruled out the election which Theresa May has just called, and her snap election will force a snap decision on quite a lot of MPs: should they stay, or should they go?

The first point to make is that an election now means returning 650 MPs, cancelling the proposed cull which would have downsized the Commons to 600 seats...so those who had faced being squeezed out in that process will get a five year reprieve (assuming, of course, the voters re-elect them) and it will be interesting to see if the promise of fewer MPs is included in the next Conservative manifesto.

With an election not expected 'til 2020, only handful of honourable members had signalled their intention to depart.

Now, others who have been wrestling with health problems or eying alternative employment, or simply battling with ennui, will have just days to decide whether they want to seek to continue in the Commons until 2022. Enquiring constituency parties will want to know.

With a maximum of seven working days left to the 2015 parliament, the time-line now looks like this:

Wednesday 19 April - the debate on an early dissolution of Parliament. By the end of the day, the clock will be ticking on the short, eventful life of the 2015 Parliament. The day's other major event will be Prime Minister's Questions, the penultimate confrontation of the Parliament, and, given the suggestion that there might not be TV debates between the party leaders, this confrontation and the one on 26 April will become major campaign events in their own right.

Over the ensuing week, Parliament will have to finalise or bin the remaining legislation still passing through Westminster…

There are a few bills at ping-pong stage at the moment bouncing between the Lords and Commons in search of final agreement. What normally happens in these circumstances is that the government seeks as much agreement as possible, and drops controversial parts of the legislation to get the rest through - a process known in Westminster slang as the "washup".

And on this occasion their lordships will only be sitting for four days next week, and, just possibly Tuesday 2 May - and the limited time strengthens their lordships' hand, because if they continue to object to a bill, it will fall if no agreement can be reached.

The bills in play are:

• Bus Services Bill (the big outstanding issue is whether local councils should be allowed to set up their own bus companies - the government opposes that)

• Children and Social Work Bill (peers want to remove a clause enabling the government to exempt local authorities in England from children's social care legislation requirements in order to allow them to test different ways of working to provide children's social care)

• Digital Economy Bill (issues in play include ticket-touting, the guaranteed prominence of public service broadcasters on digital TV platforms, and the creation of a commission to decide the level of the BBC Licence Fee)

• Health Services Supplies Bill

• Higher Education and Research Bill (the Lords inserted an amendment on the immigration status of students)

• National Citizen Service Bill

• Neighbourhood Planning Bill

• Pension Schemes Bill

• Technical and Further Education Bill (there are Lords amendments on careers advice and benefits for apprentices under 20)

A big question mark hovers over the Finance Bill. The normal drill on these occasions is that controversial bits are stripped out of necessary legislation, to get it through. In this case, there might be some watering down of its proposals on probate fees.

The Local Government Finance Bill (which devolves business rates), the Prisons and Courts Bill and the Vehicle and Aviation Bill are all likely to be dropped because they have not passed far enough through the parliamentary process - but if the government is returned, they will probably be reborn, phoenix-like, and fed into the parliamentary machine once more.

Meanwhile in select committee land, the committees will be engaged in a similar process, finishing off the reports they can produce in time, and possibly binning some inquiries that cannot be completed before the music stops.

And watch out for another, more subtle dimension to their washup, the effect of an imminent election. Opposition MPs will want reports that can be used to bash the government, while government MPs will want to avoid that, and maybe crowbar in some backing for government policy. The end result will probably be reports that are far more bland and carefully phrased.

Tuesday 2 May - the final sitting day available to the Commons and Lords.

Wednesday 3 May - dissolution day, which will take place at one minute past midnight. Assuming all legislative business is complete, it would be possible for Parliament to be prorogued - in effect suspended - a little earlier, if there is nothing to keep MPs there, so the actual dissolution would be a formality.

Thursday 4 May - Local and mayoral elections and (possibly) the Manchester Gorton by-election. These suddenly become a rather tantalising amuse-bouche for the main event, and the projected vote share for the parties could influence the unfolding campaign. (It is up to the returning officer in Manchester to decide whether the parliamentary by-election goes ahead - or whether the contest is held alongside the general election.)

Thursday 11 May (4pm) - deadline for nominations. We should already have a good idea who is going, and who is running, but a few surprises may be sprung. Might some big names be deselected by their local parties?

Monday 22 May - deadline for registering to vote

Thursday 8 June - polling day.

In the following days, a new Cabinet and team of ministers will be appointed - again it will be very interesting to see who is chosen and who is rejected.

There's no date set for the state opening of the new Parliament - I can speculate that it might be 14 or 21 June.

But this will be the moment when the new government unveils its legislative programme, and a new slate of select committee chairs and members will probably not be in place until just before Parliament's summer holiday.