One of three people killed in a helicopter crash in County Down was a personal friend of the Prince of Wales, Clarence House has confirmed.
Charles Stisted, Ian Wooldridge, and their pilot died when the aircraft hit the Mourne Mountains on Saturday.
Mr Stisted, 47, was chief executive of the Guards Polo Club at Windsor.
Clarence House said Prince Charles, the Duchess of Cornwall, and Princes William and Harry were "shocked and deeply saddened" by news of the crash.
Those who died were from south-east England and included the pilot and two passengers. The men were in Northern Ireland for a day of shooting in County Fermanagh.
'Thoughts and prayers'
Air accident investigators will catalogue and remove evidence. A police spokesman said significant resources were dedicated to the recovery.
The helicopter is believed to have taken off from Enniskillen, County Fermanagh, and crashed at about 1600 BST in an area known locally as Leitrim Lodge, between Hilltown and Rostrevor.
Mr Stisted was appointed secretary of the Guards Polo Club, located in Windsor Great Park, in 1995, and oversaw its change from a military to a civilian-run organisation a decade ago.
A Clarence House spokesman said: "The Prince of Wales, the Duchess of Cornwall, Prince William and Prince Harry are all shocked and deeply saddened by this terrible tragedy.
"Their Royal Highnesses' thoughts and prayers are with the families of those killed at this dreadful time."
Mr Wooldridge, who was also a Guards Polo Club member, is a prominent figure in Harcourt Developments, the Dublin-based company involved in the development of the Titanic Quarter in Belfast.
The medium-sized Agusta helicopter, capable of carrying up to eight people, was based at Redhill in Surrey, with a US registration and so is likely to be privately owned and run.
South Down MP Margaret Ritchie said she was "very saddened" to hear of the crash.
"On behalf of the people of South Down and those I represent, I offer my deepest and most heartfelt sympathies to the families of the bereaved at this most tragic time," she said.
Michelle Gildernew, MP for Fermanagh and South Tyrone, said the shock of the accident "has been felt by people right across County Down and County Fermanagh".
"This is a shocking and tragic accident and my sympathies go out at this time to the families of those who have lost their lives," she said.
In June last year three men were killed when their light aircraft crashed into a field near a private landing strip at Kilkeel, County Down.
Pilot Hugh McKnight, who was a 53-year-old former police officer, was returning from the TT races in the Isle of Man with Andrew Burden and Stephen Annett, both aged 24.