Do by-election results in Britain matter?

Political superlatives were being thrown around like confetti on October 20th, after two by-election victories for Labour in safe Tory seats. In Mid Bedfordshire Labour set a new record for overturning the largest absolute majority in a by-election. In Tamworth the party bettered its huge by-election victory in the same town in 1996, just a year before Tony Blair’s landslide general-election win. Is history set to repeat itself?