"It's mind-boggling. I didn't think it was possible at all," von Essen told the TT news agency. "I was so surprised when I saw I was in the lead."
Not only did he get to take the gold medal home, he broke the points record at the Memory World Cup. Among his feats? Memorizing as many binary numbers – which reached the thousands – in the span of 30 minutes.
The World Cup has ten different memory tests of which four were won by Jon Essen. He had been aiming at winning at least one of the sporting categories.
"I never thought I'd be able to beat Johannes Marlow from Germany. He's been competing for nine years and has been unchallenged for a long time," von Essen said.
The Swede has dedicated four to five hours a day in the months leading up to the London event. But he took the last week before the competition off, to let his brain relax.
"It's a mental sport, so how you feel is important," he explained.
Von Essen told The Local last year that using images is the trick to a sharp memory.
"The secret is to think of a picture. For example, a 2 looks like a swan, an 8 like a snowman and 4 like a sailboat," he explained.
"After that, it’s just a matter of making a story. So 284 might be a swan throwing a snowman at a sailboat. The more ridiculous it is – the easier it is to remember.”