Ace, companion to the seventh Doctor in Doctor Who. Keith Barnfather suggested to Aldred that she take on the role of Lisa Deranne after Elisabeth Sladen dropped out, but she wanted to play a more feminine character instead after three years of playing Ace in Doctor Who. Rory O'Donnell as Nikos, Mari's fiancé and the son of a wealthy industrialist. In love with Mari, he is first stunned by the Sontarans and later killed by them when he attempts to overpower them with their stun ray. The Rutan later takes on his form before killing Mari. Shakedown was O'Donnell's first acting job, he later appeared in the fan production Auton 3 before becoming a casting director. Michael Wisher as Robar, the ship's engineer. Robar is the first to be killed by the Rutan whilst in the engine room. Wisher had appeared in a few Doctor Who stories in the classic series, but was best known in fandom for being the first actor to play Davros, the creator of the Daleks. Wisher also had appeared in a number of fan-made productions in the 1980s and 1990s, including Wartime and The Airzone Solution. Shakedown would be Wisher's last work as an actor as he died the following year. Terrance Dicks was reportedly not happy with Wisher's decision to play Robar with an American accent. The role of Robar was originally mooted for Brian Miller, the husband of Elisabeth Sladen, although her withdrawal from the project meant he did not eventually get involved. Toby Aspin as Commander Steg, the leader of the Sontaran force chasing the Rutan. Although initially antagonistic to Lisa Deranne and her crew, he sacrifices himself to destroy the Rutan and save the ship at the story's conclusion. Aspin would later appear as another Sontaran in "Mindgame". Tom Finnis as Lieutenant Vorn, Steg's second-in-command. Slightly dimwitted, he is killed by the Rutan. Finnis would later appear in the fan production The Few Doctors, which Kevin Davies also directed. Production The film was shot almost entirely on location aboard the Second World War-era Royal Navy light cruiser , permanently moored at Symon's Wharf on the River Thames since 1971. Some scenes were also shot at Pinewood Studios. Filming aboard the vessel was frequently plagued with sound problems which caused the film crew to rapidly fall behind schedule. The unlicensed nature of the Dreamwatch production meant that they could not even refer