What was the actual proportion of the faces on that beach missing from the movie? Was it 1:2, 1:10, 1:100, 1:1000 or 1:10000 or 1:100000?

~1:250 - 1:500 depending on what sources you use.

The movie is a commercial enterprise not the agent of government policy, designed to direct public attitudes.

It would have been government policy if it had some sort of positive discrimination, let's say. But in this case we're talking about a plain lie, which doesn't seem justified from an artistic point of view...

How likely was one to stumble upon a non-white British soldier on the beach at Dunkirk?

Did you read the article? Based on their numbers, at least 10% odds.

> in this case we're talking about a plain lie, which doesn't seem justified from an artistic point of view...

It wasn't a documentary. The movie was a fantastic bit of story telling (IMHO) and I think it's one of the best movies I've seen this year.

What is the lie exactly?