Millie Bobby Brown has a "healthy" and "adult" relationship with Henry Cavill. The pair play brother and sister in 'Enola Holmes'

Millie has opened up about their friendship, insisting they have a strong bond despite their 21-year age difference, applauding the 39-year-old 'Man Of Steel' star for being "strict" with her.

"With Henry, it feels like a real adult relationship. Like a really good friendship, a really healthy one. One that we have terms and conditions. I know Henry. He has terms and conditions with me."

The 18-year-old actress told that one of Henry's conditions is that she's banned from asking him about his private life.

She added: "I’m not allowed to ask about his personal life. It’s like, ‘Millie, shut up. No.’ And I’m like, ‘Understood'."

She went on to insist her relationship with Henry is very different to her friendship with the rest of the young cast on her Netflix show 'Stranger Things'.

"I would say Henry ... is a problem solver. He’s a very rational man. Me, I’m a bit manic. I’ll try everything in order to solve something. Whereas he usually just gets it dead on right ... "

Millie also explained they have a special dynamic because Henry doesn't have any sisters in his family.