"You read the scripts and you see all these adventures and you think 'Whoa, I'm going to get to do all this!'" he said. "It's definitely a boy's dream making it. Especially all the fantasy elements, which I love. To be a part of it is really good fun."
And who can blame him? In the Arthurian world of jousting knights, saving damsels, and slaying dragons it doesn't sound like a tough day at the office. Of course, film-making is far less glamorous behind the scenes.
"I thought 'wow I get to walk into a big cave and act with a dragon', but in actual fact you get to walk onto a small set and talk to a green screen. So I'm just talking to a marker, like an X, on a green screen."
Playing the voice of the dragon is esteemed actor John Hurt. But even here Morgan doesn't always get to work with the actor.
"John records all his stuff weeks before so I've got basically a playback of his conversation. You could have somebody else reading them but it's great to have him there in spirit. It really, really helps.
"Having actors like this really adds a lot of gravity to the cast. When you see people like Richard Wilson and Anthony Head and you have the chance to work with them, you feel quite privileged really."
"Our series is very much 'Merlin: The Early Years!'" he laughs. "Everyone knows who Merlin is, the great warlock. There's been some stuff written about him, his birth and a vast amount as an older man. But there's this huge gap in between that hasn't been explored. It's great to be given free rein and have a bit of fun on that."
The look for Merlin is also quite lavish, with period costumes and huge sets all filmed before a backdrop of Pierrefonds castle in France. Ironically, producers were unable to find a suitable castle in the UK.
"Somebody said to me 'yeah the series is great and that CGI castle looks so real!' It's just about the only thing that isn't CGI!" he said.
"I've never seen anything like this in the UK, so to have it as a character in its own right is great."
Merlin screens 6:30pm Sundays on TEN.