Cartwright was born in Cape Town, South Africa, but grew up in Johannesburg where his father was the editor of the Rand Daily Mail newspaper. He was educated in South Africa, the United States and at Trinity College, Oxford.
Cartwright's birthplace was Cape Town, South Africa, but he spent his childhood in Johannesburg, where his father worked as the editor of the Rand Daily Mail newspaper.  He received his education in South Africa, the United States, and at Trinity College, Oxford.