John Krasinski was sure he had ''married up'' when a customs agent in London didn't believe he was married to Emily Blunt.

The 38-year-old actor has been married to the 'Edge of Tomorrow' actress - with whom he has four-year-old Hazel and 21-month-old Violet - since 2010, and believes he has managed to find a wife that is way out of his league.

Speaking during an appearance on 'The Tonight Show starring Jimmy Fallon', John said: ''I married up, and don't I know it.''

The studio audience erupted into applause at the mention of Emily's name, and John then revealed he was told by a customs agent that he was lucky to have bagged the English beauty.

He added: ''They don't have to tell me; the customs agent in London did.''

The 'Office' star was visiting Emily in London whilst she was filming for upcoming movie 'Mary Poppins Returns' - in which she will play the eponymous nanny - earlier this year when he had the run in with the ''surly'' man at the airport.

He recalled: ''It was going great, the customs, the whole experience. And then I hit this guy who was about my age. He looked like he was ready to get a little surly with me.

''He said, 'It says here that you're an actor. Would I know you from anything?' And I went, 'You know, we redid the U.K. version of 'The Office'.' Strike one! He was like, 'Oh, you took what we did, perfect.'

''And then he says, 'Who are you visiting here?' And I was like, 'My wife'. He says, 'Oh, is she an actress? Would I know her?' And I said, 'I don't know man, her name's Emily Blunt.' And he goes like this, 'You? You married Emily Blunt?'''

John revealed the customs agent eventually let him through, but not without looking disgruntled as he stamped the star's passport.