This is not a drill! Apple TV has confirmed that Olivia Cooke will reprise her role as Sid Baker in the hotly anticipated sixth season of Slow Horses.  The hit espionage thriller, which stars Sir Gary Oldman as Jackson Lamb, the cantankerous leader of a disgraced team of MI5 agents, returns on Wednesday, 16 September.  © Apple TVOlivia Cooke will return in the new season A newly released trailer gives fans a glimpse of the gripping new season, which sees Jackson Lamb determined to find out why his spies are being killed off one by one – seemingly by two mysterious attackers played by MyAnna Buring and Kyle Soller. Olivia’s return was confirmed in the trailer, which ends with River stunned to see Sid at the top of a staircase.  Sid appeared in the first season of the show but was seemingly killed off after being shot in the head. However, Roddy Ho later discovered that Sid’s records had been mysteriously wiped, hinting at her survival.  © Courtesy of AppleGary Oldman reprises his role as Jackson …