Complex sentence: Educated at University College School in Hampstead, London and Balliol College, Oxford, he had a Jewish upbringing; but in 1892, while at Oxford he renounced all religious belief, writing to his mother to inform her.
Split into simpler sentences: Educated at University College School in Hampstead, London and Balliol College, Oxford. He had a Jewish upbringing, but in 1892, while at Oxford he renounced all religious belief, writing to his mother to inform her.