Caleb "Cal" Knight is a fictional character from the BBC medical drama Casualty, played by actor Richard Winsor.

Winsor's casting was announced alongside George Rainsford who was hired to play Cal's brother Ethan Hardy.

Executive producer Oliver Kent has called the character consistent because when faced with trauma, Cal gets drunk, sleeps with women and makes a fool of himself.

Winsor made his final appearance as Cal, following his on-screen death, in the series thirty-one episode "Reap the Whirlwind − Part Two", broadcast on 29 April 2017.

George Rainsford was cast to play Cal's brother Ethan Hardy and it was revealed that both characters would arrive to fill job vacancies at Holby City hospital.

Casualty's executive producer Oliver Kent stated that "the arrival of Ethan and Caleb will instantly change the dynamic of the ED.

"[1] The character made his first on-screen appearance in the series twenty-eight episode "Brothers at Arms", which was broadcast on 18 January 2014.

[6] They added "Cal exudes confidence to get what he wants, but, occasionally, his bravado slips and he has to dig a little deeper to find out who he really is."

[8] Cal thrives in an adrenaline-fuelled situation and writers tend to include him on treatment teams following big accidents.

He recalled the experience as "fantastic", climbing into the limousine and acting out a medical procedure he tried to learn fifteen minutes before the cameras began recording.

[13] Producers created a romance storyline for Cal alongside guest character Taylor Ashbie (Sarah Jayne Dunn).

Soon after her arrival she gains Cal's attention and he begins involving himself in her treatment despite it being Zoe Hanna's (Sunetra Sarker) case.

Executive producer Oliver Kent later announced that Dunn would reprise her role as Taylor again and appear in late 2015.

[17] Casualty producer Erika Hossington announced a new story for Cal and Ethan which focuses on their family history and played out in the final quarter of 2015.

She told Daniel Kilkelly from Digital Spy that "we've been planning this for a year - it's a very in-depth story and it will strike at the heart of their sibling relationship."

The actor was also pleased with the "real gift" writers had provided in uniting Cal and Ethan following Taylor's damaging scams.

Writers had planned for Senior Charge Nurse Charlie Fairhead (Derek Thompson) to be Cal's confidant and Ethan to remain oblivious for a greater number of episodes.

[19] Cal decides to track down his biological mother with the aim of collecting maximum information about his adoption and Ethan's maternity.

[19] The actor later reflected on the storyline, stating "this story has a real domino affect, from Taylor, the baby, and now to this revelation about the adoption, and the question 'are Ethan and Cal brothers?'

[23] Emilie Groome (Carol Royle), a character suffering from Huntington's disease is revealed to be Cal and Ethan's mother.

[24] A writer from Inside Soap revealed that Cal's relief of locating his mother is out-weighed by anger he feels because she never contracted him warning him about the hereditary disease.

"[28] On 7 February 2017, Sophie Dainty of Digital Spy confirmed that the cast and crew had been filming a funeral for a regular character.

The show's producer Erika Hossington also confirmed that a "very shocking" event would happen after another character is involved in a car accident.

[29] This led to speculation that Lily Chao (Crystal Yu) would die after she was involved in a hit and run during the episode broadcast on 22 April.

[31] Of his decision to leave the show, Winsor said "I've had a wonderful time, but after three and a half years of doing great storylines, I decided that I wanted to find new challenges and explore new places in the world.

"[31] Winsor told Dainty that after informing the producers that he wanted to leave, he agreed to stay for a further four months, as they came up with his Cal's exit storyline.

[33] Charles Dale and Tony Marshall also reprised their respective roles as Big Mac and Noel Garcia for the episode.

[40] Holly Wade from the Radio Times branded the character a "womaniser", an "incredibly confident and an instinctive doctor" and a "constant annoyance" to Ethan.

Baylis accused the show of disregarding viewer intellect and uttered he would trust stupid Cal to treat him in hospital.

[45] An Inside Soap writer opined that Cal's break-up with Taylor marked the first time the "lothario" had his heart broken.