Caleb "Cal" Knight is a fictional character from the BBC medical drama Casualty, played by actor Richard Winsor. He first appeared in the series twenty-eight episode "Brothers at Arms", broadcast on 18 January 2014. Winsor had previously auditioned for a role in Casualty's spin-off show Holby City. Producers were impressed and recalled him to read for the part of Cal. Winsor's casting was announced alongside George Rainsford who was hired to play Cal's brother Ethan Hardy. The pair had to pass a screen test together as producers were looking for a strong sibling chemistry. Cal's role in the show is a Specialist registrar in emergency medicine. He was originally introduced as a locum. The medic is played as a lothario and womaniser type character. He can manipulate those around him with cha