"I mean I can do it when I'm very relaxed, and with good friends, then I think I can be amusing"

Rowan Atkinson is suggesting that he can be entertaining when he is in a relaxed and comfortable environment. He implies that he is most likely to be amusing when he is surrounded by buddies. This recommends that he is more positive in his capability to be amusing when he is in a familiar and comfy setting. He is suggesting that he is most likely to be successful in making individuals laugh when he is in an unwinded and familiar environment. This might be translated as him being more comfy in his own skin and being able to express himself more freely when he is surrounded by individuals he knows and trusts. It could also be interpreted as him being more positive in his capability to make individuals laugh when he is in an unwinded and comfy setting.