Utopia star Fiona O'Shaughnessy has confessed the darkness of what her character goes through in the show made her feel "joyous".

The Irish actress stars as Jessica Hyde in the acclaimed Channel 4 drama about members of an online comic book forum forced to go on the run from a mysterious and dangerous organisation known as The Network, to save the manuscript of a cult graphic novel called Utopia. Utopia, written by Jessica's father, was believed to contain the secret to the Janus virus, which would stem global overpopulation via mass sterilisation. But the virus is actually hidden in Jessica's DNA.

The first series saw Jessica murder and fight to keep alive, and the second series is set to get even heavier with her taken prisoner.

Fiona said: "When the material is dark, or when the conditions under which your character are living or surviving are dark or challenging, quite often the actor is joyous, and I felt that.

"I felt that during that time... I felt quite clean. I guess the stuff was just coming through me and I was in really good hands. Great company, great crew, excellent people."

Dennis Kelly's show, which also stars Alexandra Roach, Geraldine James, Nathan Stewart-Jarrett and Adeel Akhtar proved to be a hit.

But Fiona admitted during shooting on the first series, no one knew what to expect.

She revealed: "We didn't know what we were making the first time round!

"I was like, 'Well I strangled a guy in a public toilet today, I'll be home at the weekend, I love you... what is going on?!'

"I think we were all really surprised [by the show's success].

"I was surprised when I saw it because it just looked so... I didn't know how it was going to look and I loved how it looked."

:: Utopia returns to Channel 4 with a double bill on Monday, July 14 and Tuesday, July 15.