Mr Dobrowolski was a Ukrainian who reportedly defected from the Red Army to become the Nazi’s chief informant in the region of Chernihiv.
Ms Metreweli never met her grandfather as he stayed in Nazi-occupied Ukraine while his family fled the Red Army liberation of the region in 1943.
The documents held in Freiburg, Germany describe how Mr Dobrowolski was dubbed ‘Agent 30’ by his Nazi commanders.
Born to a German-Polish father and a Ukrainian mother in 1906, the Daily Mail reports he hated the Soviet Union when his family’s estate was seized after the 1917 revolution.
He joined the Nazis in 1941, and was paid a monthly wage of just 81 Reichsmark, around £250 today, for spying.
In letters to his Nazi officers, he signed off “Heil Hitler” and said he took part in a massacre of Jewish people near Kyiv.
The Daily Mail reported that there are also accounts of him looting the bodies of Holocaust victims and laughing at the sexual assault of female prisoners.
The Soviets put a 50,000-rouble – the equivalent of £200,000 today – bounty on Mr Dobrowolski and labelled him “the worst enemy of the Ukrainian people”.
Canadian parliament will give this guy his own day when they hear about him