<P> Filming began in April 2015 for a third series, which began screening in January 2016 . This series saw a change in format; with all six episodes covering a single story, written exclusively for television . This was the first series not to adapt any of Cleeves' novels . Ciarán Hinds and Anna Chancellor were among the new cast members for this series . A fourth series was announced by the BBC in July 2016 . Again, this series is a single story played out across six episodes, again written exclusively for television . This series began broadcasting on 13 February 2018 . </P> <P> During the filming of the programme, the cast and crew are usually based in Glasgow and other areas of mainland Scotland . Filming often takes place in areas with landscape or buildings reminiscent of those on the Shetland Islands, such as Kilbarchan in Renfrewshire, Barrhead, where Henshall was born and grew up, Ayr and Irvine, North Ayrshire . Filming locations on or near Shetland have included Lerwick, the main port of the Shetland Islands and on the NorthLink ferry approaching Lerwick . </P> <Ul> <Li> Douglas Henshall as Jimmy Perez, detective inspector (Series 1--) </Li> <Li> Alison O'Donnell as Alison' Tosh' MacIntosh, detective sergeant (Series 1--) </Li> <Li> Steven Robertson as Sandy Wilson, detective constable (Series 1--) </Li> <Li> Lewis Howden as Billy McCabe, police sergeant (Series 1, 3--) </Li> <Li> Erin Armstrong as Cassie Perez, Jimmy's stepdaughter (Series 1--) </Li> <Li> Mark Bonnar as Duncan Hunter, Cassie's biological father (Series 1--) </Li> <Li> Anne Kidd as Cora McLean, forensic pathologist (Series 2--) </Li> <Li> Julie Graham as Rhona Kelly, procurator fiscal (Series 2--) </Li> </Ul> <Li> Douglas Henshall as Jimmy Perez, detective inspector (Series 1--) </Li>

What is the relationship between perez and hunter in shetland
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