The new series has Dan and Helen exploring the Pennines from his home in Sheffield to her childhood home in Cumbria, meeting locals along the way. But it meant Dan had to beat his other fear - heights - when he had to abseil into a dark cave called the Alum Pot in the Yorkshire Dales.
He said: "There was a point at which you have to walk back and just step off the edge of this little cliff into a 100m-deep cave. "At one point, I slipped and for half a second it felt like I was falling into the cave, which I'll be honest was probably the worst half-second I've experienced in the last few years."
Co-presenter Helen was uncharacteristically anxious for Dan as he made his descent. "To give you an idea of how scary it was, even Helen was worried and she doesn't worry about anything," he said.
The pair met when she was a daredevil Blue Peter presenter and they both worked on the show's Big Olympic Tour in 2012.
