The twentieth series of the British medical drama television series Casualty commenced airing in the United Kingdom on BBC One on 10 September 2005 and finished on 26 August 2006.
Jane Dauncey continues as series producer for this series.
The series ran for 48 episodes, including two multi-episode crossovers with Holby City, broadcast as Casualty@Holby City. The two-parter series opener "Holding On", which features a block of flats collapsing, aired on consecutive Saturday and Sunday nights.
The twentieth series of Casualty features a cast of characters working in the emergency department of Holby City Hospital and Holby Ambulance Service. Fifteen cast members from the previous series reprise their roles in this series.
Simon MacCorkindale stars as emergency medicine consultant and clinical director Harry Harper, Susan Cookson as specialist registrar in emergency medicine Maggie Coldwell, Liz Carling plays associate specialist Selena Donovan and Elyes Gabel as senior house officer Guppy Sandhu. Suzanne Packer continues her role as emergency nurse practitioner Tess Bateman with James Redmond as senior staff nurse John "Abs" Denham. Georgina Bouzova and Janine Mellor portray staff nurses Ellen Zitek and Kelsey Phillips. Ian Bleasdale stars as operational duty manager for Holby Ambulance Service Josh Griffiths. Martina Laird, Will Thorp and Matthew Wait continue their role as paramedics Comfort Jones, Woody Joyner and Luke Warren with Rebekah Gibbs starring as ambulance technician Nina Farr. Luke Bailey continues as healthcare assistant and Tess's son Sam Bateman with Derek Thompson as clinical manager Charlie Fairhead.
Mark Bonnar makes his debut as senior staff nurse Bruno Jenkins at the start of the series. Ben Price arrives in episode 15 as corporate director Nathan Spencer. Thorp departs the series in episode 18; producers axed his character after failing to connect with viewers. Bonnar departs the series in episode 25, concluding a brief appearance in the show's cast. Actress Sam Grey joins the series in episode 32 as receptionist Alice Chantrey. Wait leaves in episode 39 with his replacement Kip Gamblin joining in episode 41 as paramedic Greg Fallon, described as a "man's man who likes to live life to the full, loves nature and is into extreme sports". Gibbs exits the series in its final episode, choosing to leave Casualty in order to start a family. The actress stated "It has been an honour to work with such a professional team in front of and behind the camera".
Episode 18 is part of a two-part crossover with Holby City and features the following Holby City regulars:
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