The `Brighton Rock` actor - who tied the knot with actress Alexandra Maria Lara in August 2009 - admits he is a "romantic" and liked the idea of proving his love for the German beauty in front of other people.
He said: "Both of our parents are still married and I`m a romantic. I like the idea of declaring my undying adoration in front of people. I`m an actor, of course, so I like to show off."
Sam met Alexandra when they worked on `Control` - a biopic of Joy Division`s late frontman Ian Curtis - in 2007 and the British actor admits their scenes together were among the most enjoyable he has ever done.
He told Britain`s Elle magazine: "Was it unprofessional to date my leading lady? Well, it was my first film so I didn`t know any better. Those are the only kissing scenes I`ve ever really enjoyed in a movie. I won`t go into details-"
Sam and Alexandra currently live in Germany and the actor insists he has no desire to move back to his home town of Leeds, North England.
He explained: "I couldn`t really take a girl from Berlin to live in Leeds. I love it here. I miss the Yorkshire sense of humour and things like bitter and Yorkshire puddings, but I can still get my hands on salt `n` vinegar crisps."