Boris Johnson has triggered a bumper byelection bonanza – I studied 148 past contests to find out what we can expect

The UK is facing three byelections in constituencies all vacated within 24 hours of one another. Former prime minister Boris Johnson announced he was leaving parliament with immediate effect on June 9, leaving his Uxbridge and South Ruislip constituents in need of a new MP. His vocal supporter Nadine Dorries had resigned as an MP just hours before in what appears to be a linked case, triggering a byelection in Mid Bedfordshire. And the day after Johnson’s departure, another MP quit. This time, it was former Cabinet Office minister Nigel Adams. A byelection will go ahead in his Selby and Ainsty constituency in North Yorkshire.