How old are the Pevensies in The Lion the Witch and the Wardrobe by C. S. Lewis?

Before the beginning of the novel, the Pevensie children lived in London with their mother, while their father was fighting in the war.

At the very beginning of The Lion, the Witch, and the Wardrobe they were sent to live in the country, to be away from the bombings that were happening in London.

This happened to many children during the war- they left London to live with strangers in the country, which was safer than living with the constant bombings.