Episode P1.15

Alan and his script writers have long been aware that tinkering around in the prequel season’s timeline may have consequences incompatible with the events in the canon ten ‘later’ seasons. Drawing a lesson from Star Trek’s ‘Kelvin timeline’, they hope that a bit of time travel and a suitable initial disaster related to the original episode will enable the next season of the prequel to sit broadly in the same narrative universe as notionally later seasons but unconstrained by the niceties of consistency. 

Sadly the accident they have picked may have been a bit of a nuclear option.