Mark Wilcox was a scientist working in the Hastings area during World War II on a top secret biological warfare experiment involving anthrax. When DCS Christopher Foyle of the Hastings police was investigating some suspicious deaths in the area, Mark wanted to do the right thing by the local inhabitants even if he was possibly exposing military secrets.
Mark had a twin brother named Tim who was flying with the RAF. Captain Jack Harkness of Torchwood (Cardiff division) knew him back then during the war. He thought that even though Tim was a poor pilot, he was a very good navigator. Should he ever get shot down, he would always know where he was. Both Mark Wilcox and Tim (no last name given) were played by Peter Sandys-Clarke.
So this theory of relateeveety creates a possible link between 'Foyle's War' and 'Torchwood'.