The handsome star spilled all on the Graham Norton Show on BBC 1 tonight.
He bravely opened up about going naked and the perils of wearing a tiny pouch to protect his modesty for the explicit sex scenes.
Dornan said: “On set I wore a wee pouch to keep everything in. I was given a selection – for size I guess – and when I found one that fitted I took it off and noticed inside a label that said, ‘Inmate number three’ – clearly it had been worn before! I just had to grin and bear it.”
But that wasn’t even the most embarrassing moment…
Dornan was sharing the chat show sofa with Dame Helen Mirren, Liam Neeson and singer-songwriter Sigrid.
Dame Helen has certainly been no stranger to raunchy scenes throughout her career but it was Dornan’s other revelations that had the entire studio in stitches.
The Irish star confessed the excrutiatingly awkward truth behind the sexy shots of him striding out of the sea.
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Dornan said: “What you can’t see is that it was pebbly and I couldn’t walk on it. The beach was only semi-closed and there were lots of people taking photos as I struggled up the beach. It was so not cool.
“They even put down a piece of carpet for me to walk on but I still struggled. In the end, I had to wear a pair of jelly sandals and no one looks sexy in those!”
Incredibly that STILL isn’t his most embarrassing confession of the night which involves the painful removal of fake pubic hair…
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Dornan said: “I was quite small and wasn’t hairy at all (when) I was 15 and looked seven. On one particular day, I was in an amateur drama play and was going to a party after. For my role, I had bits of a black wig glued to my face for a beard and I decided to keep it for the party so I would look older.
“I also decided to cut up the rest of wig and glue it to my private parts just in case I got lucky. I didn’t get lucky and removing the bits of wig ripped out the very small amount of natural hair I had down there. It was a physically and emotionally painful experience!”
The Graham Norton Show is on BBC One on January 19 at 10.35pm.
Fifty Shades Freed is out on February 9.