Turing and Clarke had met previously since Turing was friends with Clarke 's older brother .
In the spring of 1941 , Joan Clarke developed a close friendship with her colleague from Hut 8 , Alan Turing .
Alan Turing and Clarke had met previously since Alan Turing was friends with Clarke 's older brother .
In the spring of 1941 , Joan Clarke developed a close friendship with her colleague from Hut 8 , Alan Turing .