Mikkel Borg Bjergso, co-founder of the Danish microbrewery Mikkeller, is a man who likes a challenge. At the opening of the new Mikkeller bar in Shibuya, Bjergso tells me that his next goal is to finish the Berlin Marathon next September in two hours and 45 minutes.

"Let's bet on it," he says, sticking out his hand for me to shake.

I'm not the gambling type, but Bjergso is persuasive and tenacious. I know he went to university in the United States on a track and field scholarship, he has also launched a worldwide program called the Mikkeller Running Club and makes a pilsner by the same name. Despite this, my mind began assessing the odds.