I had 24 hours' notice and I'd missed the first series as I was working when it came out. So I bought the DVD and watched as many episodes as I could in the hours leading up to the casting.

I instantly loved the show and really wanted to be a part of it which made the audition even more nerve wracking - partly because I might get to fulfil my childhood dream of being a knight!

Rupert as Sir Leon and Nathaniel Parker as Agravaine

Sir Leon started off as a very small role. I was only meant to be in one scene jousting Arthur, but at the read-through I was given a couple more lines. I arrived on the first day of filming series two, having learned my line for that day - "The King commands your presence immediately" - and when it came to my first take I fluffed it.

I managed to get it right the next take, despite my heart pounding and all colour draining from my face. There was no way I thought that two years later I would still be in the show.

I feel immensely lucky and grateful to the producers for making Sir Leon such an integral part of Camelot. I used to say Sir Leon was the Gunther of Camelot. Gunther worked at the coffee shop in Friends and would pop up sporadically in episodes like I did in series two and three. After series four I think I may have finally surpassed Gunther!

I'd describe Leon now as the rock of Arthur's Round Table of Knights, a real A* pupil of the Camelot School, a prefect - he does everything well and to the book.

He's diced with death on a number of occasions but he always manages to bounce back unscathed! I should probably thank the druids for letting him drink from the cup of life.

Leon's been wounded in many a battle, incinerated by the Great Dragon and has still managed to return to Camelot without so much as a scar. Thank goodness he's such an incredible fighter and that he has sleeves on his chain mail - if he was dressed like Percival he might not have been so lucky!

People always ask whether the chain mail we wear is heavy. It's lighter than it would have been hundreds of years ago, but it gets weighty by the end of the day.

Elyan (Adetomiwa Edun), Sir Leon (Rupert Young), Sir Percival (Tom Hopper), Lancelot (Santiago Cabrera) and Gwaine (Eoin Maken).

The most annoying thing is that it gets filthy so when you take it off, your neck is grey, as are your hands. I have so many books I've read on set which have grey hand marks all over them!

Chain mail also conducts heat and cold, so if it's a boiling day you roast and if it's freezing you freeze too - but we are Knights, after all, so I think we can live with it.

My favourite scenes to film are the big fight sequences.

Every move is carefully rehearsed and I trained in stage combat at drama school so I'm quick at picking up the routines. The stunt coordinators are fantastic, it's their expertise that makes us look so great on screen.

I remember filming the battle with the skeletons last year and having to learn a fight with the stunt coordinator. We were tussling together and then he stepped out and they filmed me fighting nobody, but pretending there was someone there.

I felt very stupid doing the moves and making all these battle cries against the thin air. I was convinced it was all a wind up to make me look silly but of course when the Bafta-winning special effects team put their magic to it I was fighting a skeleton and it looked incredible.

This Christmas I'll be celebrating with my family and, of course, will be tuning in to see the Merlin grand finale on Christmas Eve.

It is so exciting to be concluding the series the night before Christmas. My favourite episode to watch so far this series has been Lancelot du Lac as it was so exciting and dramatic but I have a feeling episode 13 is going to go out with a bang... I can't wait!

Rupert Young plays Sir Leon in Merlin.

Comments made by writers on the BBC TV blog are their own opinions and not necessarily those of the BBC.