'Harry Potter' fans stunned over Josh Herdman’s transformation in The Games

Harry Potter star Josh Herdman has left fans stunned by his transformation.

The actor, who found fame as Gregory Goyle in the smash-hit film series, is a contestant in ITV’s The Games this week and fans can’t get over his change in physique as they watch the 34-year-old competing against 12 other celebrities.

Indeed, the Robin Hood actor has grown up since his days playing one half of Crabbe and Goyle – the Slytherin sidekicks of Draco Malfoy (Tom Felton).

Herdman now works as a cage fighter and has the looks to match, much to the surprise of viewers.

After he was seen coming in second place in the 400m sprint behind Love Island star, Wes Nelson, Herdman’s name was all over social media as fans reacted to his new look.

One fan tweeted: "Jesus Christ, Josh Herdman 😍 How did he turn into this beautiful man? OOF! "

"Josh Herdman is pretty fit now 😍," another commented.

Elsewhere, other viewers noted that the actor's green ensemble appeared to be a subtle nod to the Slytherin house in Harry Potter.

"Coincidence that Josh is wearing green? I think not," one viewer mused.

Another added: "also hats off to whoever put Josh Herdman in green 🐍"

Herdman took up martial arts and cage fighting after his time on Harry Potter as a way to combat anxiety. He then went on to make his debut as an amateur MMA Fighter in April 2016.

The Games sees the star put his fitness to the test as he joins 11 other stars battling it out in a series of live sporting events.

Read more: The Games viewers praise Max George's bravery in competing

The stars have undergone weeks of intensive training ready to go head-to-head in a range of sporting challenges in the athletics arena, the swimming pool, gymnasium and velodrome.

All have been pulled out of their comfort zones to be coached as athletes, swimmers and cyclists, to compete in the hope of coming top of the medals table and being crowned the winner of the competition.

Watch: Daniel Radcliffe reflects on 20 years of being Harry Potter