A well-regarded group of thinkers will pull others in, but conversion dates of those associated with the Thirties, he points out, were fairly evenly spread between 1910 and 1960.
In the Twenties it may have been that, after centuries on the margins of British society, the Church of Rome seemed exotic to the disaffected Modernist. The world had been rocked by war and revolution, and perhaps Catholicism looked like giving meaning and shape to the spiritually bereft Waste Land.
TS Eliot remained within an Anglican but described his outlook as "Anglo- Catholic"; Graham Greene and Evelyn Waugh both became Catholics in the late Twenties. Among clerics, Father Ronald Knox converted in 1917 and went on to serve as Roman Catholic chaplain to Oxford University.
Meanwhile, the influential Jesuit priest Father Martin D'Arcy brought the young Lord Longford into the fold, and by the middle-of-the-century figures such as Muriel Spark (1954), Edith Sitwell (1955) and Siegfried Sassoon (1957) converted.
What most of these people have in common, says Adrian Hastings, is their "social and theological conservatism", which is also true of those who have more recently crossed over.
In the Nineties, a perceived lack of order and reverence in the Church of England has created a new rush to Rome, though it was the passing of legislation enabling women to become priests in November 1992 that proved the last straw for many. Home Office Minister Ann Widdecombe publicly embraced Catholicism in April 1993. John Gummer, former Secretary of State for the Environment, converted a year later, believing the Church of England was now inviting Catholics "to transfer their allegiance to a denomination and declare their adhesion to a sect".
Instrumental in both of these conversions was Father Michael Seed, who turned away from a low church background at 18. He is ecumenical adviser to Cardinal Basil Hume and serves as an unofficial chaplain to Parliament. Other recent converts include the Duchess of Kent, Charles Moore, editor of the Daily Telegraph and long identified with the high Anglican right, and Frances Shand-Kydd, mother of the Princess of Wales. She explained that she had been attending services for six years at the Catholic cathedral in Oban, near her home, and had become familiar with their "liturgy" and "warm humanity".
Waiting in the wings is former defence minister Alan Clark, who is receiving instruction from Michael Seed. Elizabeth Hurley and the Princess of Wales have also reportedly flirted with the idea, both presumably hoping they would photograph well taking the sacrament.