Daniel Radcliffe couldn't understand why nobody wanted to try Fool's Gold sandwiches on the set of 'What If?'.

The 25-year-old actor was bemused as to why just him and another member of the crew were interested in gorging on the calorific treat - a whole loaf of bread, a jar of jam, a jar of peanut butter, bacon rashers and loads of butter - because he insists the foodstuff tasted fantastic.

He said: ''Fool's Gold was amazing. For anyone that doesn't know, it's a very large sandwich with a lot of peanut butter, jam and bacon inside it, and it is delicious.

''They obviously made some on set for the montage in which it's being made in the movie. And I don't understand why, but me and one other guy were excited to try it and everyone else was being very healthy and, frankly, gutless about it. Everyone should have tried it. It was lovely.''

The sweet treat - which late music legend Elvis Presley was also a big fan of - brought his character Wallace and his good friend Chantry (Zoe Kazan) closer together and Daniel admitted he knew the 31-year-old actress was the right person for the job because she is the ''smartest'' person he's ever met.

Speaking about casting the part of Chantry, the 'Harry Potter' star said: ''We needed somebody that, as well as being obviously very charming and funny, was also really, really smart, because her character is.

''And Zoe Kazan is one of the smartest people I've ever met - forget just actress or actor, she's one of the brightest overall. So that made working with her really easy, because she just responds to any and everything you can give her.''

'What If?' is out now on Blu-ray and DVD, courtesy of Entertainment One.