Covid-19, insiders claim. Work on the sixth season of the hit BBC drama, set in Birmingham, was temporarily paused due to 'a false positive test for a member of the crew'.
The person then took an NHS Covid test which came back negative - allowing filming to officially resume as per official protocol, a spokesperson said.
But crew members claim filming continued for several hours when the first test came in. Union Bectu is now investigating after workers felt their health was put at risk, The Guardian reports.
Filming delays for BBC One cost between £650,000 and £1million per hour. TV sets have put countless measures in place to ensure the safe return of cast and crew - including regular testing and social distancing.