Rachel Kelsey is a champion climber who survived being stranded in sub-zero temperatures in the Swiss Alps.
Rachel and her partner Jeremy Colenso were rescued after they sent an SOS by text message to a friend in London. With little food or shelter, they huddled together on a narrow ledge with a 1000 metre drop on either side for a gruelling 36 hours.
Rachel is now taking part in a Channel 4 science programme to find the country's Superhuman, the country's most exceptional man and woman. She joins Jenni to talk about being tested to the limits of human endurance.