The Peak District national park is home to some or Britain's rarest and most persecuted birds of prey.
Martin Wainwright has been following the fortunes of its breeding peregrines, goshawks and hen harriers. All these birds are strictly protected by law, but further protective measures straight out of contemporary hi-tech policing are still needed: nests are scrutinised by CCTV, "smart water" is painted around them, and DNA samples are taken from chicks to add to a national register. So why are these birds still under threat? producer Tim Dee