They were arch enemies, fighting each other for their very survival. But five years after bomber pilot William Ross was shot down and killed in the Second World War, it was a German soldier who showed compassion to the fiancee left behind.

Gernot Knop had witnessed the 28-year-old RAF sergeant’s death in anti-aircraft fire as he attacked a Nazi fuel ship.

And writing in English to Dorothy Bird, he told her of Sergeant Ross’s heroic last mission and returned to her the few possessions he had with him when he died at a seaport in eastern Libya in 1941.

Showing the respect troops on opposing sides had for each other, the letter told how he was buried by his enemies with ‘military honours’ and was saluted for his bravery by Field Marshal Erwin Rommel, leader of the German forces in the North Africa campaign.

The letter began: ‘This war being finished, I feel myself obliged to send you these things, which I found by the Sgt W A Ross...’

Herr Knop’s letter was sent from Hamburg on June 3, 1946. And although Miss Bird had already been officially informed of Sergeant Ross’s death, relatives said it was a comfort to her to know all she could about her ‘darling Bill’s’ death.

Herr Knop, an engineer, said of the pilot’s final seconds: ‘He flew over the rock and rushed towards the ship, but the bombs plunged into the water, and then he came in about 10m’s hight(sic) over us trying to escape.

‘I saw how one of his motors got hit and stopped. The pilot pointed at our anti-aircraft cannon to show it to his shooter.

‘In that moment the fate of the Bristol Blenheim was made sure....