Henry Cavill was left mortified when he got an erection while filming a sex scene.

The 32-year-old Hollywood star - who's best known for playing Superman in 'Man of Steel' - has admitted to becoming over-excited during filming for his breakout role as Charles Brandon in the historical drama series 'The Tudors', much to his embarrassment.

He shared: ''It's only happened to me once, and it was very embarrassing.

''A girl had to be on top of me, she had spectacular breasts, and I hadn't rearranged my - stuff into a harmless position. She's basically rubbing herself all over me and, um, it got a bit hard.''

Henry - who stars alongside Ben Affleck in the much-anticipated 'Batman v Superman: Dawn of Justice' next year - admitted the incident was ''unacceptable'' and he kept saying sorry to his co-star.

He told Men's Fitness magazine: ''I had to apologise profusely afterwards. It's not great when you're in a professional acting environment and somebody gets a boner, is it? No, not acceptable.''

Despite his own embarrassing incident, Henry is adamant there's nothing ''sexy'' about filming love scenes.

He said: ''You don't think of sex scenes as showing your bum to the nation. It's actually acutely uncomfortable being naked in a roomful of people. The very last thing it is is sexy. The actual physicality is very uncomfortable. All you're doing is smacking your nuts against someone, and nothing is going in.''