The Magician's Nephew is counted as book one these days, but that was not the order in which it was written and a few things won't make as much sense if you read it first, so I'm not sure why they re-ordered it other than they think that chronological order makes more sense overall, something I disagree with. It was originally the penultimate book, before The Last Battle.

So really, one through four were made into films, but BBC TV and Radio both did the whole thing.