A coded letter from Jewish POW Captain Julius Morris Green. Photo: Digital South / Screenshot.

Captain Julius Morris Green, a Jewish dentist from Glasgow, was captured by the Nazis at Dunkirk in 1940, and imprisoned, from 1941 to 1944, in the infamous Colditz Castle, near Leipzig, where he risked his life to send Britain’s MI9 intelligence service information via encrypted letters to his family, the UK Daily Mail reported on Friday.

A collection of 40 of the coded letters, being auctioned at Bonhams, in Knightsbridge, London, on June 18, is notable because “they highlight an important part of what was going on in World War II,” Simon Roberts, a specialist in the book department at Bonhams, told the Daily Mail.

“The risks he was running, as a Jewish prisoner-of-war in Nazi hands, hardly bear thinking about,” Roberts said. “Under the surreal humor of his letters lies horror and quite extraordinary bravery.”

Green gleaned his information during visits as a dentist to treat other patients and German troops. His letters contained information about the camps, strategic details about German shipping and troop movements, and lists of useful materials for potential escapes, the Daily Mail said.

The letters were sent to his family then decoded by MI9, an intelligence branch whose job was to communicate with and aid resistance fighters, to try and rescue soldiers trapped behind enemy lines, and to establish links with British POWs to send them advice and equipment, the Daily Mail said.

In one letter, from November 1943, Green wrote to his father about an imaginary girlfriend: “Phillipa appears quite the most winsome lass, but don’t get frightened, she’s not my type! I think that I’m a great deal too slow for her & anyway, I could never marry a girl whose idea of enjoyment is to dance until 3am every night.”

Decoded, the letter reads: “Making diesel only petrol a failure.”

Captain Green was born to a Jewish family in 1912, in Killarney, County Kerry, graduated from the Dental School of the Royal College of Surgeons in Edinburgh and practiced dentistry in Glasgow before the war.

In 1939, he joined the Territorial Army and was posted to the 152 (H) Field Ambulance of the 51 Highland Division, which was captured at St. Valery, in northern France during the retreat to Dunkirk, in June 1940. He spent the remainder of the war in Nazi camps Blechhammer, Lamsdorf, Sandbostel, Westertimke and Heyderbreck.

After the war, his papers were held by the Imperial War Museum in London and he later wrote a bestselling book about his experiences entitled ‘From Colditz in Code.’

Green died in September 1990.