The twenty-first series of the British medical drama television series Casualty commenced airing in the United Kingdom on BBC One on 23 September 2006 and finished on 4 August 2007.
Jane Dauncey continues as series producer for this series until Episode 21 where Oliver Kent takes over.
Series 21 marks the twentieth anniversary of Casualty with this series consisting of 48 episodes. To celebrate the anniversary, the two-part opening episode "Different Worlds" features several characters traveling to Cambodia to assist at a medical clinic, where long-standing figures Charlie (Derek Thompson) and Duffy (Cathy Shipton) are reunited. Filming took place in Phnom Penh from 22 May to 8 June 2006 with cast and crew contending with intense heat and challenging conditions. Shipton later commented on the experience stating "Cambodia is a beautiful country with gracious, dignified people. I have made many good friends and we keep in touch with email."
The series features 2 further two-parter episodes, "The Sunny Side of the Street" (episodes 17 & 18) and "Combat Indicators" (episodes 27 & 28).
The twenty-first 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. Derek Thompson stars as clinical nurse specialist Charlie Fairhead. Suzanne Packer continues her role as emergency nurse practitioner Tess Bateman with Georgina Bouzova, Janine Mellor and James Redmond portraying staff nurses Ellen Zitek, Kelsey Phillips and John "Abs" Denham. Ian Bleasdale stars as operational duty manager for Holby Ambulance Service Josh Griffiths. Martina Laird and Kip Gamblin continue their role as paramedics Comfort Jones and Greg Fallon. Luke Bailey stars as healthcare assistant and Tess's son Sam Bateman, Ben Price returns as corporate director Nathan Spencer and Sam Grey as receptionist and later healthcare assistant Alice Chantrey.
Multiple arrivals and departures occur this series including the return of some familiar faces. Cathy Shipton reprises her role as Lisa "Duffy" Duffin for the first two episodes set in Cambodia as part of the shows twentieth anniversary celebrations. Shipton stated "IâÂÂm thrilled to be working with Derek again. It feels as though Duffy has never been away." Jane Hazlegrove and Joanne King arrive in Episode 3 as paramedics Kathleen "Dixie" Dixon and Cyd Pyke. Gerald Kyd makes a guest return as senior house officer Sean Maddox in Episode 5 for five episodes.
Laird departs in Episode 10 commenting "I'm very lucky to have had the opportunity to work with such wonderful people and play such a great character for five years." Bouzova departs in Episode 16 after her character Ellen is killed off. Matt Bardock makes his debut as paramedic Jeff Collier in Episode 25, initially for three months until Episode 39, before returning as a regular in series 22. Daphne Alexander arrives in Episode 26 as staff nurse Nadia Talianos with Peter O'Brien joining as consultant Theo "Stitch" Lambert in Episode 38. Bailey leaves in Episode 38 with O'Brien and Carling departing at the conclusion of the series. Carling decided to quit the show because she felt like a "workhorse" and wanted change in her life following the death of a close friend.
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