Author Len Deighton has passed away, and his obituary on the BBC mentioned his novel SS-GB (1977) (I read it in the 80s, and saw the miniseries maybe 8~9 years ago) predated fellow alternate history Fatherland (by Robert Harris, 1992) by multiple years.

I thought “surely The Man in the High Castle (1962) and The Iron Dream (1972) preceded both” and started wondering when was the first alternate history with a Nazi victory.

Turns out it was in 1937! The book was Swastika Night by Katharine Burdekin (although she used the pen name Murray Constantine & the author’s true identity was only uncovered in the mid-1980s).

It has been described as “the most original of all the many anti-fascist dystopias of the late 1930s” and contains many elements seen a decade later in George Orwell’s Nineteen Eighty-Four: the past has been destroyed and history is rewritten, language is distorted, few books exist apart from propaganda, and a secret book is the only witness to the past.

• Internet Archive - Swastika Night