Second comment on the article The Volunteer: Jack Fairweather’s Auschwitz spy thriller wins Costa prize, by David Sanderson, The Times, January 29 2020.
I should add that the first book presenting Witold Pilecki’s role was Fighting Auschwitz: the Resistance in the Concentration Camp by Józef Garlinski (1913-2005), Polish officer who was also imprisoned in Auschwitz. The book was published in 1975. Garlinski was tattooed with the number 121 421.
From Garlinski’s obituary in The Telegraph, December 1, 2005:
“Most strikingly, he established the importance of Witold Pilecki, the army officer who had himself arrested in order to set up a military organisation inside the camp and co-ordinate a rising with an outside attack that never came; Pilecki later escaped and survived the war, only to be executed by the Communist government.”
Garlinski’s father was a POW in the Soviet Union, following the September 1939 campaign and was murdered by the Russians in Katyn in 1940, along with thousands of other Polish officers.