Contrary to popular belief, Broadchurch is not based on or a remake of Danish show The Killing, and the script for Broadchurch actually predates The Killing by at least five years. Chris Chibnall originally had the idea for Broadchurch and started working on the script in 2002, however, it took him ten years to get the show on air.
The first season has numerous links to another British TV programme - Doctor Who. Writer Chris Chibnall wrote a number of episodes and Euros Lyn and James Strong have directed various episodes of the show. The cast includes Who regulars David Tennant (10th Doctor) and Arthur Darvill (Rory) as well as guest stars Olivia Colman (The Eleventh Hour) and David Bradley (Dinosaurs on a Spaceship, also written by Chibnall). Bradley also played William Hartnell (1st Doctor) in Adventure In Time And Space. Jonathan Bailey also guest stars in Doctor Who as Psi in Time Heist.
Several actors have been regulars or guests in the Harry Potter film series: Alfred Enoch, who has a tiny role as a reporter, played Dean Thomas throughout the Harry Potter films (also, Dean Thomas is the name of Chloe's boyfriend). David Tennant (DI Hardy) played Barty Crouch, JR in HP and the Goblet of Fire. David Bradley (Jack Marshall) played Argus Filch throughout the HP film series. Carolyn Pickles (Maggie Radcliffe) portrays former Hogwarts professor Charity Burbage (who is then murdered by Voldemort) in The Deathly Hallows Part 1.
Several actors in Broadchurch have made appearances in the popular teen show 'Skins.' Olivia Coleman (Detective Miller) appears in the third and fourth season as Naomi's mother Gina. Pauline Quirke (Susan Wright) plays a detective in seasons 4 first episode and Jacob Anderson (Chloe's boyfriend) appears in generation 3's episode 'Mini'
The trivia item below may give away important plot points.
Almost all of the actors in season one took their parts with the understanding that they might be Danny's killer. Only Jodie Whittaker, who played the victims mother, was told definitely that she wasn't (and she wasn't told who was). Acording to creator Chris Chibnall, "Jodie asked me around episode six of series one, 'Am I a grieving mother or a secret killer crying crocodile tears?' I told her it wasn't her, but only then."