Formally "The Receiver for the MetropolitanPolice District", the Receiver is in fact the financial manager of the MetropolitanPolice -- in legal terms the Treasurer of the Metropolitan Police Fund. THe name derives from the duty of the original Receiver (John Wray) to "receive" from the parishes of the MetropolitanPoliceDistrict those monies raised on the rates for the maintenance of watchmen and constables prior to 1829.
Fido, Martin, and Keith Skinner. The Official Encyclopedia of Scotland Yard. Rev. and updated ed. London: Virgin, 2000.