Giant's Bread by Agatha Christie

On a day in July Sebastian Levinne walked along the Embankment in the direction of Jane's flat. It was a day more suggestive of early spring than of summer. A cold wind blew the dust in his face and made him blink.

There was a change visible in Sebastian. He had grown perceptibly older. There was very little of the boy about him now -- there never had been much. He had always had that curious maturity of outlook which is the Semitic inheritance. As he walked along now, frowning to himself and pondering, he would easily have been taken for a man over thirty.