When fans of Call the Midwife spotted Olly Rix’s name popping up in Casualty coverage, they probably didn’t expect such a high‑profile new chapter. But on February 10, 2025, the BBC officially announced that Rix would be joining the Holby City emergency department as Clinical Lead Consultant Flynn Byron, in the upcoming twelve‑part Casualty arc Internal Affairs

From Poplar to Holby: a compelling leap
Olly Rix previously played Matthew Aylward in Call the Midwife, beloved husband to Nurse Trixie (Helen George). His character was written out in 2024, heading off to New York—closing a significant chapter for the actor . Now, Rix returns to medical drama—but this time into a very different world.

The Casualty announcement describes Flynn Byron as “charming but complicated”, a former Special Forces medic stepping into civilian medical life. Fresh from a tour of duty, he’s determined to make change in an NHS weighed down by bureaucracy, while wrestling with trauma and an undisclosed deception that could threaten his future in Holby ED

A dramatic debut in Internal Affairs
Flynn Byron’s first appearance arrives on Saturday 15 March 2025, in Everything Changes. The story notably uses point‑of‑view filming to show medical emergency from Flynn’s perspective—rattled, wounded, yet clinically sharp and deeply conflicted. Accompanying the main story are high‑stakes arcs, including Stevie Nash’s shocking news and Dylan Keogh grappling with personal turmoil

Rota reveals that Flynn makes his debut early in the Internal Affairs box‑set: episode 1 on 15 March, then episode 2 the following week—each tackling corporate corruption, internal power struggles, and the emotional toll on ED staff

“Radically different” role, and a full‑time commitment
In an exclusive Radio Times interview published 15 March 2025, Rix described Casualty as a “radically different” experience from his previous roles, praising the show’s writing, tone, and realism , He also disclosed that he underwent rigorous physical and weapons training with former Special Forces operators to deepen his portrayal of Flynn’s military‑honed instincts—a preparation he finds “all‑consuming”

When asked about his future on the show, Rix was definitive: “Flynn isn’t going anywhere… we’ve filmed for a year and you’ve only seen ten episodes. We’ve 40‑something in the bank now”. In short: this is no brief cameo but a full‑blown new regular.

A disruptive force in Holby ED
Executive Producer Roxanne Harvey has characterised Flynn’s arc as dramatic and resonant, exploring themes like the emotional toll of NHS decision‑making and the possibility of redemption in the face of past mistakes . Fans have also learned from What to Watch that Flynn arrives directly into the middle of clashing with senior surgeon Russell Whitelaw (guest‑starring Robert Bathurst), who turns out to be his father‑in‑law—complicating everything both personally and professionally

Flynn also has history with consultant Stevie Nash (Elinor Lawless). They knew each other from medical school, and their prior relationship exposes buried tensions, especially as Flynn tries to institute change in the ED’s routines and hierarchies

What fans are saying
The announcement triggered excitement across fan forums and social feeds. On Reddit, long‑time viewers hailed him as a welcome new face—and a surprising crossover for Call the Midwife audiences . Some fans quipped gleefully: “He’s so leng—nobody’s more leng than Dylan, but Flynn might give him a run for his money” . Others discussed how to dive into Casualty, recommending the Internal Affairs box‑set as a jumping‑on point with minimal past context needed