Is there any evidence of it being rigged, don't know, but there may be a very easy way to find out to see if it was rigged or at the very least point a strong finger of suspicion in that direction, all that's needed is for the postal ballots to still exist or if they don't still exist then for the result of the postal ballots to still exist, which I bet it does, at the end of the day its just a few numbers.
Remember, Labour won by a whisker, so if the postal ballots don't more or less (by a few percentage points) reflect that result then I think its fair to say that that result is suspicious.
Not that there will be any real enthusiasm to do that of course, even on that of the Tories, and here's why, there was two sighs of relief when Labour won that by-election, one by Labour and an even bigger one by the Tories, the last thing the Tories want right now is for the Brexit party to start winning seats.
You or anybody else stands no chance of finding out if that by-election was rigged, no chance.
So much for our democracy.