SOLVED. Adult British novel set in the 1950s or 60s about a man who is being asked to substantiate a miracle in which his brother in law the pope saves a baby's life. [s]

[Peter]

British Novel set in the 1950s or 60s about a man who is being asked to substantiate a miracle in which his brother in law saves a baby's life. The BIL becomes pope and the baby later becomes a cult leader who murders his congregation including a relative of the narrator. The narrator lives in Malta and the novel features a character who becomes Bishop of Gibraltar

I suspect this is a classic but I can't find it using search or AI

[Becca]

Earthly Powers by Anthony Burgess?

[Peter]

That’s the one! Many thanks.