Tamzin Outhwaite worried she'd have a heart attack filming 'Freeze the Fear' stunt

Watch: Holly Willoughby says she was "in tears" filming Freeze the Fear

Tamzin Outhwaite was scared she'd suffer a sudden heart attack while plunging into a frozen lake during filming for new BBC show Freeze the Fear with Wim Hof.

The 51-year-old former EastEnders star performed the stunt as part of the new reality series, in which Dutch motivational speaker Wim Hof puts celebs through physical and mental challenges in extreme cold.

Read more: Freeze the Fear called "tone deaf" amid heating crisis

Outhwaite told the People's Love Sunday magazine: "My mum died of a very sudden heart attack and, in my head, jumping into ice-cold water could trigger something like that.

"My main fear was: ‘Am I going to have a heart attack when I hit the water?’”

The show requires its celebrity participants — including singer Alfie Boe and Strictly Come Dancing's Dianne Buswell — to go through various extreme tasks, including jumping into the lake beneath eight inches of ice.

Outhwaite said that, despite the dangerous nature of some of the stunts, she enjoyed the experience and felt she was being looked after on the set.

Read more: Tamzin Outhwaite reveals menopause struggles

"I trusted everyone with my emotions. I just felt like I’d had a meditation and I definitely felt a sense that my mum was around, which was a lovely, warm feeling," said the actor.

She added: "What I’ve come back with is much more respect for my own fortitude. My strength is much better than I imagined.

"You can do much more than you think. You can challenge yourself more, so I think what I’ve learnt is that I’m strong." 

Freeze the Fear with Wim Hof launched on the BBC earlier this week and is presented by Holly Willoughby and Lee Mack.

Read more: Tamzin Outhwaite swears off boozy nights out

It focuses on Hof's famous techniques for exposure to cold, yoga and breathing, which have led him to set several Guinness World Records for cold-related stunts.

Alongside Outhwaite, the show's celebrity line-up features Alfie Boe, Chelcee Grimes, Dianne Buswell, Gabby Logan, Owain Wyn Evans, Patrice Evra and Professor Green.

Watch: Amanda Holden and Tamzin Outhwaite go punting