The Little Britain funnyman was planning to fly to New York to discuss a joint adventure with his TV star pal Bear Grylls but his Dutch partner Lara Stone put a stop to their plan to go rock-climbing together.
Walliams tells Britain's Radio Times, "It was only scaling a rock face, but Lara got really upset and said no."
The comic admits the blonde beauty, who he married in 2010, became an emotional wreck as she cheered him on during his marathon river swim, which left him with severe back problems and a stomach bug.
He adds, "I didn't like to see her upset, but it was great having her support. She actually had her driving test on the day I got ill, so she heard it on the radio and was doubly upset she hadn't been there to look after me."