Police said today that no charges will be brought over the alleged killing of two rare birds of prey on one of the Queen’s estates.

A warden and two other walkers said they saw two hen harriers killed while in flight on the Sandringham estate in Norfolk where Prince Harry and two others were shooting. The prince denied all knowledge of the event.

Now the Crown Prosecution Service (CPS) says there is insufficient evidence to bring any charges in relation to the deaths of the birds, which are protected by law but face persecution on many estates. No remains of the dead birds were found.

Norfolk police said: “The bodies of the hen harriers have not been found and there is no forensic or ballistic evidence. Witnesses also heard unexplained shooting in the area before the three suspects said they were present at the scene, so other people cannot be ruled out. The three suspects, who were interviewed by police, all denied that the birds were killed by them.”

There are only 20 breeding pairs of hen harriers in Britain. The Royal Society for the Protection of Birds (RSPB) said: “We regard the killing of hen harriers as one of the most serious of wildlife crime offences. We would always hope that people killing hen harriers are brought to justice.

“We believe the illegal killing of hen harriers is the reason for this bird's low UK population, especially in England where only 20 pairs remain.

“Despite a thorough and swift investigation by the Norfolk Constabulary, the RSPB is disappointed there is insufficient evidence to proceed with the investigation.”