To someone who didn't know her, that smile might have looked almost natural.

He was still smiling at me, but the smile didn't look real anymore.

In fact, a smile could sometimes look sad, he couldn't stand seeing himself at all.

He seemed truly happy to see her, and his smile looked genuine.

A smile doesn't look all that 'natural on his face, though.

The smile looked as if it might stay on his face for ever.

Sometimes his smile in response must have looked wan indeed.

His smile was a little crooked, but looked real enough.

Gordon Brown's smile does not look at home on his face.

His smile looked forced, but Barton gave him points for trying.