The teenager dubbed "the next Jessica Ennis" is still coming to terms with the fact that she will be competing against the present Jessica Ennis when the Olympic heptathlon competition gets under way today.
"It's surreal," Katarina Johnson-Thompson says, stealing a sideways glance at Ennis. "I'm normally at home watching Jess in the major championship heptathlons on TV, getting excited by the build-up.
"The night Jess got the gold in Berlin and [Usain] Bolt got the 100m world record [at the 2009 World Championships], I'd just come back from Alton Towers. I just got in when Jess was on the second lap of the final event, the 800m."
Ennis chuckled at the thought. The 26-year-old goes into the Olympic competition as the world No 1 in her event but she knows that, in the long-term scheme of things, the 19-year-old roller-coaster rider is gaining ground on her.
At the TNT Fortuna heptathlon at Kladno in the Czech Republic in June, Johnson-Thompson achieved an Olympic "A" standard qualifying score with 6,248 points, improving the British junior record she had taken from Ennis six weeks previously and missing Carolina Kluft's world junior record by a mere nine points. Two weeks ago she added the world junior long jump title to her burgeoning CV, jumping a wind-assisted 6.67m at Montjuic Stadium in Barcelona.
Asked in June whether the Liverpool Harrier with the double-barrelled name could be the next Jessica Ennis, the original replied: "I'm sure she will be… She'll be better.
"It's brilliant that she's qualified for the Olympics. I'm sure she'll do really well. But I think it'll be in the next couple of years that she'll start getting closer and closer… I'll probably retire then."
For the time being, though, Johnson-Thompson is happy to be making her Olympic debut as a team-mate of the favourite. "Everything's happened so fast," she says. "Everything's just snowballed. It's happened at once.
"I can't believe I'm here, getting ready for the Olympics, but I'm calm about it. I don't think it'll sink in until I get to the stadium.
"Yeah, at the moment I'm relatively calm about everything… I don't know why."