As a teenager, she and her siblings converted to Catholicism, following the conversions of their parents. Her "maternal grandparents were Unitarians – a non-conformist faith with a strong emphasis on social reform ...". In response to criticism of her writing about Oliver Cromwell, she has said, "I have no Catholic blood". Before his own conversion in his thirties following a nervous breakdown in the Army, as she explains, "My father was Protestant Church of Ireland, and my mother was Unitarian up to the age of 20 when she abandoned it."