The 72-year-old film-maker was so desperate for his adaptation of CHARLES DICKENS's classic novel to look authentic, he insisted upon the strict diet - but Clark insists he still had fun.
He says, "When I went to Prague (Czech Republic) for the screen test Polanski just looked me up and down and said: 'Barney, if you do get the part, you won't be able to eat any sweets or chocolate.' I had to have a hollow face."
But the cheeky 12-year-old admits, "I used to sneak the occasional sweet into my room. Luckily he (Polanski) made up for it by letting me go go-karting."