What pen name did C.S. Lewis use for his 1933 book The Pilgrim’s Regress?

C.S. Lewis published The Pilgrim’s Regress under the pen name Clive Hamilton.

The Pilgrim’s Regress, published in 1933, was Lewis’s first published work of prose fiction. Its full title, The Pilgrim’s Regress: An Allegorical Apology for Christianity, Reason and Romanticism, signals its connection with John Bunyan’s The Pilgrim’s Progress while also presenting Lewis’s own intellectual and spiritual journey.

Lewis used “Clive Hamilton” rather than his familiar initials. “Hamilton” was the surname of his mother’s family, and “Clive” came from his childhood name. He later used another pseudonym, N.W. Clerk, for A Grief Observed, published after Joy Davidman’s death. Those two pen names are therefore easy to mix up: Clive Hamilton belongs to The Pilgrim’s Regress, while N.W. Clerk belongs to the book of mourning.