"Plenty." Guppy says. "Which is one of the many reasons why we must under no circumstances lose the kit bag."

He stops and undoes the bag, brings out three double sized mars bars and passes one to each of the others.

"I've been topping it up as we go along, we can have something more substantial when we get safe."

If all else fails, he has some nutition pills that will keep them alive, but aren't exactly tasty.