They have provided a bird's-eye view of some of Scotland's most spectacular landscapes.

But the use of drones without prior agreement is now set to be banned over estates and property owned by The National Trust for Scotland.

The heritage body is the latest to bring in guidelines to protect their properties, wildlife and visitors.

Thousands of the flying devices have been sold across Britain, offering photographers the chance to capture spectacular images.

But the NTS, which owns the double Unesco World Heritage Site of St Kilda, the Isle of Canna and Culzean Castle, in Ayrshire, among its 129 properties says it wants anyone deploying drones to seek prior permission.

It is particularly concerned about the threat to wildlife - especially during the breeding season. St Kilda has 1 million seabirds - including internationally important colonies of gannet, fulmar, kittiwake, guillemot and puffin.

St Kilda is Europe's most important seabird colony, and one of the major seabird breeding stations in the North Atlantic.

Canna in the Small Isles also has sea eagles.

The NTS, which also owns and maintains the islands of Iona and Staffa, confirmed it was bringing in restrictions to protect people and animals from being disturbed by unmanned aircraft.

A spokeswoman said: "The trust-wide policy that's been introduced in recognition of the fact that there are more and more drones commercially available.

"The trust recognises that new technologies like this can be a good way of exploring our heritage and the places in our care, however, there can be risk of damage to property or disturbance to wildlife, livestock and visitor enjoyment from inappropriate use.

"Essentially, the policy says that drones are only allowed with the permission of the property manager, as per the Scottish Outdoor Access Code.

"The policy also outlines the considerations that need to be made in deciding whether or not to give permission - such as the impact on natural or cultural heritage, the Civil Aviation Authority requirements for small unmanned aerial vehicles. Operators also need to have adequate public liability insurance in place."

In the run-up to Christmas, the head of Britain's most northerly model flying club has also warned about the dangers of people buying drones as presents and instantly becoming a danger to the public.

Martin Hayes, chairman of Dornoch Model Flying Club, said that enthusiasts were spending as little as £100 on the machines without any idea of the legalities involved in flying the aircraft outdoors.

He had witnessed one person fly an expensive drone at the golf driving range in Dornoch and break the law four times!

"He had spent £1500 on the device and didn't know what he was doing. It was totally illegal," said Mr Hayes.

He also pointed out the case last year of a TV-repair shop owner who became the first person convicted in the UK for "dangerously" flying a drone saying the fine and legal costs would bankrupt him.

Robert Knowles, 46, of Barrow-in-Furness, was fined £800 and ordered to pay costs of £3,500 at the Furness and District Magistrate court after being prosecuted by the Civil Aviation Authority (CAA). He pleaded guilty to flying a small unmanned surveillance aircraft within 50 metres of a structure and flying over a nuclear installation, the BAE System submarine-testing facility.

The CAA said that the case raised important safety issues concerning recreational flying of unmanned aircraft, which is legal as long as it is done away from built-up areas and structures.

Mr Hayes said the British Model Flying Association - in consultation with the CAA - laid down strict rules to its member clubs, who operate miniature fixed wing aircraft.

But many drone operators seemed oblivious of the legal requirements such as not flying above 400 feet.

The problem was such that next April the CAA were planning a "drone awareness month."

Historic Scotland has also said unauthorised drone activity at its 345 properties was "strictly prohibited".

Growing concern has led to Historic Scotland, which maintains Edinburgh and Stirling castles, to draw up aerial restrictions.