Main cast •
Martin Shaw as Mr. (later Prof.) Robert Kingsford, Head of Department/Clinical Consultant (Series 1–4) •
Niamh Cusack as Dr. Christine Fletcher, Senior House Officer/Consultant/Director of Critical Care (Series 1–4) •
David Harewood as Dr. Mike Gregson, Registrar (Series 1–3) •
Esther Hall as Dr. Louise Macken, Senior House Officer (Series 1–3) • Paul Warriner as Dr. Stuart Phelan, Senior House Officer/Registrar (Series 1–3) • David Partridge as Dr. David Scobie, Senior House Officer/Trauma Surgeon (Series 1–3) •
Jane Slavin as Cathy Jordan, Ward Sister (Series 1–3) • Katie McEwen as Judy Enshaw, Charge Nurse (Series 1–4) •
Connor McIntyre as Terry Harker, Charge Nurse (Series 1–4) •
Kim Vithana as Yvonne Silver, Ward Sister/Trauma Nurse (Series 1–3) •
Dominic Mafham as Dr. Andrew Argyle, Paediatrician (Series 2–3) •
Tamzin Malleson as Dr. Kate Brady, Senior House Officer (Series 2–3) •
Jane Danson as Samantha Docherty, Nurse Practitioner (Series 3–4) •
Michael Kitchen as Mr. Jack Turner, Trauma & Orthopaedic Surgeon (Series 3–4) •
Silas Carson as Dr. Raz Amin, Anaesthetist (Series 3) •
Jaye Griffiths as Dr. Ruth Cole, Senior House Officer (Series 4) •
James Murray as Dr. Danny Barton, Senior House Officer (Series 4) •
Michele Austin as Poppy Jonston, Ward Sister (Series 4) • Don Gallagher as Dr. Jeffrey Drummond, Clinical Director (Series 4) •
Emily Hamilton as Dr. Saskia Walker, Senior House Officer (Series 4) • Ben Taylor as Dr. James Da Costa, Registrar (Series 4)
Additional cast •
Con O'Neill as Kenny Fletcher, Relative (Series 1) •
Catherine Russell as Issy Howell, Relative (Series 1–2) •
Neal Trotman as Paul Gregson, Relative (Series 1–2) • Leon Trotman as Richie Gregson, Relative (Series 1–2) •
Alan Williams as Martin McMad, Patient (Series 1–2) • Andy Quine as Dale, Paramedic (Series 1–4) • Naomie Thompson as Tricia, Paramedic (Series 1–4) • Josh Moran as Josh, Paramedic (Series 1–3) • Lisa Rigby as Jane, Paramedic (Series 2–3) • Dean Williamson as Alan, Security Officer (Series 1–2) • Bill Rodgers as Freddie, Security Officer (Series 1–2) •
Cathy Tyson as Stella Gregson, Relative (Series 2) • John Lloyd Fillingham as Steve Moore, Relative (Series 3) •
Parminder Nagra as Sunita Verma, Hospital Café Staff (Series 4) •
Ronny Jhutti as Ajay Verma, Porter (Series 4) • Bhasker Patel as Raj Verma, Hospital Café Manager (Series 4) •
Judy Holt as Jean Kenning, Receptionist (Series 4) •
Amanda Abbington as Tessa Bailey, Relative (Series 4) ==Episodes==