A night to remember: How to plan your election viewing

At one point earlier this year it looked as though Election Night 2010 might be a rather subdued affair.

Around a quarter of Returning Officers wanted to delay the count in their constituencies until the following day, to save money and reduce the risk of error through exhaustion. But swingometer addicts insisted that the loss of excitement was too high a price to pay. Eventually, after months of lobbying by the all-party Save General Election Night campaign, the Government backed a Conservative amendment to the Constitutional Reform and Governance Bill (finally enacted in the dying days of the last Parliament) which requires parliamentary election counting to start "within four hours of the close of the poll, save in exceptional circumstances".

With the election as delicately balanced as any in living memory, even half-hearted enthusiasts may have cause to feel grateful for this decision tomorrow night. Most major broadcasters offer extensive coverage (from 9pm on Sky News and from 9.55pm on BBC1, ITV1 and BBC HD), and there is also unprecedented scope this year for experiencing the drama online – not to mention the mind-boggling scope for all-night Twitter commentary).

But it remains problematic to decide when, if at all, to go to bed: partly because extensive boundary changes make it impossible to make anything but the vaguest predictions of what will happen when but also because, in such a close race, the crucial turning-points could turn out to be almost anywhere.

None the less, past experience suggests that key moments in the night are likely to include the following:

10pm

Let the counting begin

Polling stations close, and broadcasters reveal their exit polls. These have recently been fairly accurate, but have been known to get it badly wrong (for example, in 1992, when they wrongly predicted a hung parliament, and in October1974, when calculations based on exit polls predicted a Labour majority of 144 – rather than the correct figure of three). Those itching for an excuse for an early night may take a confident exit-poll-based verdict as their cue for turning in, but if the race looks close you won't want to place too much confidence in them. In any case, where's the fun in not stretching the process out for as long as possible?

10.45pm

The first result?

The earliest result announcements will be imminent by now. These have tended to come from the Labour heartlands in the north-east in recent years, with Sunderland South being the first seat to declare its result for each of the past four general elections (a win for Labour's Chris Mullin in each case). But boundary changes have altered a number of constituencies in those parts, and Sunderland South has been absorbed into the new constituency Houghton and Sunderland South. So the honour of being the first to declare cannot go to the usual winner.

11.30pm

Early marginals

Results from some relatively marginal constituencies begin to trickle in from now onwards. For example: Torbay (about 11.40pm – although remember that all times are even more approximate than usual); Wolverhampton South West, Battersea, Putney (between 12.30 and 1am); Peterborough, Ilford North (about 1am). Putney produced the first surprise of the night in 2005, with the Conservatives reclaiming the seat they lost in 1997.

1am, 7 May

Goodbye, Gordon?

A sighting of Gordon Brown might be expected from now onwards: his constituency, Kirkcaldy and Cowdenbeath, declared its result at 1.10am last time. But it will be too early for him to react with any confidence to nationwide trends. Watch out too for East Renfrewshire and Blackburn, where Jim Murphy and Jack Straw, respectively, are a tiny bit less safe than Cabinet ministers ideally like to be; and for Tooting, which the Conservatives could win with a 6.1 per cent swing from Labour. If Tooting turns blue, an overall Cameron majority is a distinct possiblity.

2am

Clegg-time

The redrawing of many constituency boundaries makes it harder than usual to predict which results will arrive when. But it's safe to assume that a number of significant results will be arriving around this time, including the marginal Kent seat of Gravesham. Nick Clegg's seat, Sheffield Hallam, declared at 2.12am in 2005.

2.30am

Were you still up for Balls?

If recent general elections are anything to go by, the overall result will be becoming clear, with the remaining interest being largely concerned with individual contests or the fate of individual candidates. For example, will Hazel Blears (who didn't come out of the expenses scandal spectacularly well) hang on to her theoretically safe seat in Salford and Eccles? And could Ed Balls, in Morley and Outwood, conceivably provide another "Portillo moment", if the Tories were to achieve a 10.5 per cent swing?

But recent general elections probably won't be anything to go by, not least because of the LibDem factor. Talking of which, watch out for Aberdeen South, which the Liberal Democrats could take from Labour with a 1.6 per cent swing. If they do, it will mean that the night is going very well for them – which might suggest a hung parliament.

3am

The Luton moment

Luton South declared its result at 2.58am last time. It will be worth watching this time. Not since 1950 has a party won this seat in a general election (or one of its predecessors, Luton East and Luton) without going on to form the next government.

This time, with Labour's Margaret Moran standing down after the expenses scandal, and Esther Rantzen complicating matters as an independent candidate, the Conservatives need a 7.4 per cent swing to win – the kind of percentage swing that they need nationwide to win an overall majority. (Talking-point: if Ms Rantzen wins the seat, does that imply that she will form the next government?)

Another interesting result may come in around now from Dorset West, where the Liberal Democrats are seeking their own version of the "Portillo moment" via the high-profile scalp of Oliver Letwin – for which they would require a 2.3 per cent swing.

3.30am

All eyes on Cameron

David Cameron's constituency might be declaring its result around now. It is possible that enough will now be known about the national picture for what he says and does at the declaration to be of some interest. But he is unlikely to linger, as he will want to get down to London as soon as possible.

More interest might attach to the result from Brighton Pavilion, where Green leader Caroline Lucas has a realistic chance of becoming her party's first MP. The impact of such a breakthrough would be huge: representation in Parliament would bring funding, access to the airwaves and a boost in credibility that could easily be translated into more seats in future. Conversely, failure to win would be a devastating blow to morale that could destroy political momentum that has taken years to build up.

4am

The battle for Barking

Similar calculations will be going through the head of the BNP's leader, Nick Griffin. He's standing against Margaret Hodge in Barking – and would require a stonking 16.5 per cent swing to defeat her. Such an outcome can be all but discounted – except that, in the current climate, almost anything is possible.

Other results expected around this time include Richmond Park, which Zac Goldsmith is attempting to win for the Conservatives from the Liberal Democrats, and Derby North, where the Liberal Democrats need a 7.3 per cent swing to win the seat from Labour. A LibDem victory here might reasonably be taken as a sign that the night has been one of Lib Dem triumph and Labour disaster.

4.30am

The Speaker cornered?

In 2005, the main battle was over by now. Labour won its 324th seat – enough for a majority – at 4.28am, in Corby. Michael Howard had conceded defeat seven minutes earlier. This time, the question of who will form the next Government – or whether or not Parliament will be hung – could remain unresolved It might, however, be worth going to bed at this stage. Counts in Northern Ireland, which includes several marginals, won't even begin until later in the morning. And there are bound to be a few recounts to delay a final result still further.

But there will still be plenty of interesting things happening in individual constituencies. For example: Tessa Jowell, Liam Byrne and Ben Bradshaw are arguably a little bit vulnerable in, respectively, Dulwich and West Norwood; Birmingham Hodge Hill; and Exeter. And there should be plenty of colour at the declaration at Bethnal Green and Bow (where Labour's Rushanara Ali and Respect's Abjol Miah are staging their own version of 2005's epic battle between Oona King and George Galloway).

5am

A Pennine watershed

The Yorkshire seat of Colne Valley has been identified as another key battleground in the struggle between the Liberal Democrats and Labour. If the Liberal Democrats win, with a swing of 5.9 per cent, it will be taken as a sign that the LibDem surge was more than just a passing phenomenon. Then again, if that's the case, you'll probably have gathered that by now.

5.30am

The end in sight

If things are still in the balance, the result from Brentford and Isleworth (which might come in around now) may clarify the picture. A key marginal, being defended by controversial Health Minister Ann Keen, it's eminently winnable by the Tories.

7am

All over bar the recounts?

Those who decided to go to bed earlier and catch up first thing in the morning may well be congratulating themselves, while the up-all-night brigade will be wondering what to do next. If the final balance of power in Parliament really does depend on the last few seats, the tension could continue well into the day, and beyond. In 2005, Harlow, the final seat (excluding South Staffordshire, where the poll was postponed), didn't declare until 11.40am on the Saturday after the election, after three recounts.

Late declarers this time are likely to include Buckingham (where UKIP's Nigel Farage is among those taking on Speaker John Bercow) and Westmorland and Lonsdale – which the Conservatives could snatch from the Liberal Democrats. But the very last in will be Thirsk and Malton, a safe Tory seat where (following the death of the Ukip candidate, John Boakes) the poll has been postponed until 27 May.