Which of Roald Dahl's books do you think transferred best to the big screen?

Yeah, just watched The Witches last night with the kids, it was the umpteenth viewing of that movie in our house. Never tire of watching it & for me it’s the best movie based on Dahl’s delightful stories. Now I realise & absolutely agree that Willy Wonka was a brilliant piece of storytelling that worked marvellously on screen, but the aforementioned movie just shades it for me. So, getting back to the question at hand. Have you a favourite movie spawned from his works & if so, which is it & why?