London’s Telegraph is reporting that Catholic novelist J.R.R. Tolkien spent three days in training with the top-secret British Government Code and Cypher School (GCCS) in March 1939.

A respected linguist, Tolkien was sought after to crack Nazi codes in the event that Germany declared war.

Tolkien’s involvement with the war effort was revealed for the first time this week in a new exhibition at GCHQ, the new name for GCCS, the government’s spy base in Cheltenham, Gloucestershire.

The director of GCCS, known only as ‘Alastair G Denniston,’ drew up a list of 50 possible candidates ‘‘earmarked for service’’ in the event of war.

Denniston was given a list of names by dons at Britain’s two leading universities, Oxford and Cambridge, of those who had worked with the government in the First World War.  Tolkien was a professor of Anglo-Saxon studies at Oxford.

Although “keen” to the idea, Tolkien eventually declined a £500-a-year offer to become a full-time recruit.

‘‘Why he failed to join remains a mystery,” said an unnamed GCHQ historian. “There is no paperwork suggesting a motive, so we can only assume that he wanted to concentrate on his writing career. ‘We simply don’t know why he didn’t join. Perhaps it was because we declared war on Germany and not Mordor.’’