The hit BBC drama about a police anti-corruption squad was forced to halt filming mid-season in March due to the coronavirus pandemic and subsequent lockdown, with Compston only having seen the first four scripts out of six episodes.
Compston, who plays DS Steve Arnott, told The One Show the first two episodes had been shot and he had read up to script four, admitting it ended on a “massive bombshell”.
The 36-year-old actor said: “Well there's a few before that as well... But just because I don't have script five, there's a big, big question at the end of [episode] four.”
Compston confirmed plans were in place to finish filming the series before Christmas. But he was not a hundred percent confident that would be possible, as the fallout from COVID-19 and the introduction of social distancing guidelines continued to impact on TV productions.
He said: “We've got a definite date that we're working towards but there's no point announcing it because the situation's so fluid, and it can change daily, so hopefully we can get it done before Christmas.
“I think there will be changes. I mean there's going to massive changes off camera just because of the protocols and the social distancing, how many people can be on set, no congregating, people off-camera wearing masks. It's going to be a completely different feel.
“In terms of the changes… we really wouldn't want to compromise the scripts, the scripts are so good, and people are so loyal to the show, there would be no point coming back if we're going to compromise quality.”
Trainspotting star Kelly Macdonald has joined the cast of Jed Mercurio’s hit drama as detective Chief Inspector Joanne Davidson, the latest police officer under investigation by anti-corruption unit AC-12.
She will star alongside Compston, Vicky McClure as DI Kate Flemming and Adrian Dunbar as Superintendent Ted Hastings.
The last series of Line Of Duty saw Stephen Graham star as DS John Corbett, an undercover police officer who was investigated by AC-12, and the identity of the elusive ‘H’ - the corrupt police officer and crime lord - again went undetected
Previous guest stars have included Thandie Newton, Keeley Hawes and Lennie James.