For Italian speakers, the above might be of interest. Raoul Paciaroni is a formidable amateur historian who usually writes about the Middles Ages but has written a couple of books about incidents in his home town of San Severino Marche in the period between the Italian Armistice and his town's liberation in July 44. Having read his book "Una Lunga Scia di Sangue", I looked for any documents on the particular individual named above. Campbell was a South African PoW who on escape joined up with local partisans and was killed in an incident on 12th June 1944. It was a War Crime and therefore investigated immediately post-war. Those investigations are held at Kew. Although the book is in Italian, its Appendices include the main documents from the file which are in English.