If you know how to sample properly then it's certainly possible to work out a result within 90 minutes provided a reasonable spread of ballot boxes have arrived, especially if the result is not too close. But I'm not sure the BBC has extensive experience of how to sample ballot boxes.
Well both parties have fought this seat seriously before so the first should be true. The BBC are of course relying on political sources, who could either be lying or the campaign is inept. Both are possible I suppose.
Corbyn's letter to MP reported in the Guardian blog:
I wanted to write to thank you for all of your work to support the byelections. At a difficult time for the party, in the midst of the article 50 debates, our MPs have led the way. Thank you for all you have done motivating members and activists, at our phone banks, supporting our candidates and, of course, hitting the doors day in and day out. Special thanks are of course due to Andrew Gwynne, Sue Hayman, Cat Smith, Jack Dromey and Ruth Smeeth, who have gone above and beyond to lead these campaigns on behalf of the Party. Myself, the PLP, and the whole of the Labour movement owe you a great debt of thanks.
We always knew that these were going to be competitive, close and challenging elections, but with your help we have made the arguments on the issues that matter to working people – our local NHS services, and an economy that works for the whole of the country, ensuring that no one is left behind. We should all be proud of the campaigns we have run, and I have extended my thanks, on behalf of the PLP, to the party staff who have put their lives on hold and worked seven-day weeks to make the case for Labour.
We will know more once the counts are underway, and of course, colleagues will be kept updated. But for now, thank you again, and I hope everyone has the chance to relax this evening after a long (and wet) day on the doorstep.
What time do you think both by-elections will declare? I have a feeling that this will be a particularly long night.
I think when the News and Star said "There's 100 boxes that have arrived here at Whitehaven Sports Centre" that means that they've all arrived, but re-reading that it could just mean that there's 100 that have arrived.
The turnout is 50%.
Don't know whether this helps more experienced hands than me estimating the declaration time.