The last case of this was when the now defunct Buckinghamshire Constabulary called upon the MPS to help in the investigation of the Great Train Robbery .
Before the 1970s , police forces often called for assistance from the Metropolitan Police because of their detective experience .
The last case of this was when the now defunct Buckinghamshire Constabulary called upon the Metropolitan Police to help in the investigation of the Great Train Robbery .
Before the 1970s , police forces often called for assistance from the Metropolitan Police because of their detective experience .