British actor Laurence Fox needed medical attention after he suffered hallucinations when he fell ill while filming a hard-hitting survival reality show.

The Gosford Park star headed to the South American rainforest to film U.K. Tv programme Bear Grylls: Mission Survive, in which a group of celebrities leave their luxury lives behind and fight to survive in the wild.

Fox was participating in a gruelling trek when he began seeing visions and became delirious, prompting him to seek help from a doctor who discovered his blood-sugar levels were dangerously low.

He says, "I was convinced there were these tiny little people trying to steal things from our rucksacks. I was shivering really badly and then I started panicking."

The show's survival expert Scott Heffield adds, "I went down to the camp and met Laurence halfway. He was delirious, hallucinating, shaking, basically talking a load of waffle. He's had some stress and anxiety - that's a cocktail for a state of delirium."