People have openly speculated on whether we'll ever know what first drew Deputy Prime Minister Nick Clegg to do a deal with the Conservative party.
However, going through the Daily Telegraph at the end of the longest day I found the simple explanation of why so many Scottish Labour MPs wanted to scupper any talk of a PR deal with the Lib Dems.
The Telegraph says that under the AV system the Lib Dems would now have 79 seats compared with the 57 they gained last week. The Conservatives would have 281 instead of 307 and Labour would have had 262 instead of 258.
According to the Electoral Reform Society if the single transferable vote was used in the General Election then the Conservatives would have had 246, labour 207 and Lib Dems 162.
A breakdown of the results showed that the regional imbalances that prevent the Conservatives and Labour being national parties would have been addressed.
The Conservatives would have had seven MPs in Scotland instead of just one, and would have had parity with the Lib Dems in Wales with 10 MPs each.
Meanwhile, Labour's share of the Scottish seats would have been reduced from 41 to 28, but there would have been gains in the south-east, the south-west and the east of England where they traditionally struggle.
That's what you read - Labour in Scotland would be reduced from 41 MPs to 28 MPs. End of argument as Tom Harris, the anti-PR, anti-coalition, stick in the mud Labour MP for Glasgow South might say.
But, as is becoming my mantra around the Harris judgement on so many other things, you have to say from a Labour point of view: "Tom was right".