London: Prince William and Harry flew to Spain on Friday for a secret hunting trip to celebrate the younger prince's graduation as a fully operational Apache attack helicopter pilot.

The royal brothers were staying on an estate in the backwaters of rural Cordoba owned by the Duke of Westminster, Gerald Grosvenor, Britain's third-richest man and one of William's godfathers, the Daily Mail reported.

Finca La Garganta, near the village of Conquista, on the border of Castilla La Mancha, is one of the largest and most exclusive hunting estates in Western Europe.

It is teeming with wildlife including wild boar and stag which William and Harry, both crack shots, are said to be keen to bag.

The brothers have visited the estate before and last time were said to have bagged a staggering 740 partridge on a single day.

The second and third in line to the throne arrived in Spain on separate flights as they are not allowed to travel together in case of an accident.

William, who was not apparently accompanied by his wife, the Duchess of Cambridge, flew into Seville while Harry arrived on a private jet at Cuidad Real Central later in the afternoon.

They took up residence in a ten bedroom villa with a group of friends and their Scotland Yard bodyguards, one of three luxurious hunting lodges built at the heart of the estate at a cost of several million pounds by the reclusive Duke.

It has marble floors, wooden beams - and its own jacuzzi and sauna.

The estate has just one - practically impassable - public road, its own petrol station and a fleet of armed security guards driving 4x4s to keep any undesirables at bay.

The 27-year-old is due to be assigned to one of the Army Air Corps Apache squadrons at RAF Wattisham in Suffolk and could be posted back to the frontline in Afghanistan by the end of the year.

The holiday is also something of a farewell for the 29-year-old, who is due to be stationed in the Falkland Islands with his RAF Search and Rescue crew for six weeks from next month.