Jacob Masters is a fictional character from the British medical drama Casualty, played by Charles Venn. He made his first appearance during the twenty-ninth series episode "If You Could Bottle It", which was broadcast on 18 July 2015. Venn's casting was announced on 13 February 2015 and he began filming at the show's studios that same week. Jacob is a former army medic turned nurse, who is given a job at Holby City Hospital after he brings a patient into the Emergency Department (ED).
Jacob is portrayed as being direct, confident, manipulative and unconventional. Jacob was given connections within the ED through fellow nurse Louise Tyler (Azuka Oforka) and consultant Elle Gardner (Jaye Griffiths). His early storylines saw him implement a "controversial" protocol in the ED, held hostage by terrorists and then shot by a police officer. Jacob is seen struggling with the IPCC's decision not to take action against the officer. The character has had an on-off relationship with Connie Beauchamp (Amanda Mealing), which became popular with viewers who gave them the portmanteau #Jonnie on social media. The couple's relationship was tested several times.
Later storylines have seen Jacob revealed as the biological father of Elle's son, Blake Gardner (Kai Thorne). In June 2018, Jacob's was given a new love interest in the form of paramedic Sam Nicholls (Charlotte Salt). Exploration of the character's background will begin in September 2018, upon the arrival of his mother Omo (Ellen Thomas). For his portrayal of Jacob, Venn won the Favourite Male TV Personality accolade at the 2016 Screen Nation Film and Television Awards. Critics have had a mixed response to the character, with Alison Graham of the Radio Times calling him "a cocky narcissist", while Elaine Reilly from What's on TV thought he had become "one of the foundations of the ED".
On 13 February 2015, the BBC Media Centre announced Charles Venn had joined the cast of Casualty as new nurse Jacob Masters. Venn began filming at the show's Roath Lock Studios that same week. Of his casting, Venn commented, "It's truly a pleasure and honour to be part of Casualty as it's such a successful long-standing medical drama. I'm keenly relishing the challenge and my time in Cardiff and I look forward to tackling the role of nurse Jacob." Shorty after he was cast as Jacob, Venn's mother told him that he would be working alongside his cousin, Azuka Oforka (who plays Louise Tyler). Venn admitted that he had no idea they were related, but called it a "wonderful surprise" and said they had worked on a storyline together. Venn filmed five months worth of scenes before they aired. He made his first appearance as Jacob during the episode broadcast on 18 July 2015.