I attach here the story of the sinking as told by Friedrich Kemnade, at the time Commander of the 3. Schnellbootflottille and later Rear Admiral, in his book "Die Afrika Flottille. Der Einsatz der 3. Schnellbootflottille im Zweiten Weltkrieg. Chronik und Bilanz", Motorbuch Verlag, 1978 (kindly lent to me by Francesco Mattesini). In the map from the book, the mine barrage just laid by HMS ABDIEL NW of Biserta which presumably caused the loss of S 35 and her entire crew is indicated by the letter "X" at the extreme right of the map.