'Turnout was high for a by-election, but still low overall, which makes extrapolation a dubious game. But, the result does suggest British politics has been turned on its head. As Sir John Curtice, the psephologist, told the BBC, "we are now in a different political world” in which domination by any one party might not be possible.
In other words, the rise of the Brexit Party could turn a huge number of seats into marginals and make any election deeply unpredictable. Which makes it really rather not a good time to hold an election if you are the governing party. Especially one that promised to deliver Brexit.'
The Telegraph