There are at least 30 unsolved murders from 2000 up to now. I doubt they are "closed" but I also doubt they each have a 30+ strong task force working on them.
And only today Sir Peter Fahy said words to the effect that missing teen searches were unsustainable to Greater Manchester Police on resource grounds.
So it does rather beg the question why the MPS continue to use considerable resources on a "crime" that comes under another country's jurisdiction.
I find it unlikely that finding Madeleine (or whatever happened to her) is the sole objective. Even though the allocated funding is attributed to OG, there are bound to be off-shoot strategic objectives involved, including rebuilding the strained relationships of the past towards more efficient cooperation in the future; mutual enlightenment as to the mysterious workings of each other's jurisdictions; possibly helping to dismantle or track known or suspected gangs of whatever sort...
The UK and Spain now seem to have built up a good working relationship in terms of hunting down wanted criminals, yet PT is just a skip and a jump away...
I doubt that all 30+ are still working full-time on the Madeleine case as such outside of any "all hands on deck" periods. Depending on the skill set, some may be working on other cases (or potentially related ones) while remaining on call, with others getting on with the case plod work. Or some of those nearing retirement may be training more junior staff or even helping PT homologues in specialist areas (or vice versa).
