If it's for a local quiz (and that quiz isn't full of lots of trick questions and red herrings), I'm reasonably confident that the answer required is, as you suggest, 'New Scotland Yard'. However the correct answer should probably either be:
(i) 'There isn't one!' (because Great Britain doesn't have a single police force) ; or
(ii) the Home Office (because that's where policies common to all forces emanate from).