Before the 1970s, police forces often called for assistance from the Metropolitan Police because of their detective experience. The last case of this kind was when the now defunct Buckinghamshire Constabulary called upon the MPS to help in the investigation of the Great Train Robbery. In 1965 the last of the Met's territorial divisions was formed and named Q (Wembley) in 1965, formed out of part of X Division. In 1966 three male Metropolitan Police officers were murdered on Braybrook Street by Harry Roberts and two other occupants of a vehicle who had been stopped for questioning. The force enlisted Norwell Roberts (its first Windrush generation black officer) in 1967, followed by its first black female officer Sislin Fay Allen the following year. 1968 saw the abolition of the groupings of divisions known as Districts, ninety-nine years after their formation. The end of the 1960s also saw the Met's old alphabetical Divisions renamed Districts and Sub-Divisions renamed Divisions.