And it wasn't foreign media or paparazzi photographers who violated the unwritten Buckingham Palace rule.

Three Canadian television crews were waiting at the foot of Blackcomb Mountain early yesterday morning when the three princes arrived for their first day of skiing here.

Crews from CBC, Global TV and VTV, a Vancouver station, were camped out at a chair lift.

At least one of the crews had been tipped off that the royals would be using the lift, one of dozens at this Rocky Mountain resort.

The spokesperson also warned that any more intrusions outside set opportunities could prompt Prince Charles to decide not to return to Whistler for any more holidays.

``If any of you (Canadian) guys screw up, there are plenty of other ski resorts around the world to choose from,'' said Charles Rae, a British photographer who has been covering the royals for the Sun newspaper for 10 years.

``We're going to stick by the rules, and we expect you guys to stick to the rules,'' Rae said after a morning media briefing yesterday by Charles' deputy private secretary, Mark Bolland.

Details of the briefing, as per royal protocol, are not for publication. But a palace spokesperson informed the media that three Canadian television crews were at the foot of the mountain and began recording images as the three princes and their security entourage arrived at the chair lift.

Mounties quickly moved the crews several hundred metres away. A palace media co-ordinator then asked the crews to stop shooting and requested that any footage of the arrival at the hill not be aired.

``I don't think they got much because they were pushed way back,'' said the palace spokesperson.

Since Princess Diana's death last August, Buckingham Palace has warned that any member of the media who intrudes on the family's privacy risks being ``named and shamed.''

It may not sound like much of a penalty, but two French photographers who stepped outside the protocol during the princes' last ski holiday in Switzerland have suffered.

One, a full-time cameraman with a photo agency, was fired after he was discovered locked in a bathroom at the top of a hill with his camera aimed out a window at the chairlift. The other, a freelancer, lost all rights to the photos he took.

``They can't put you in front of a firing squad, but there are consequences,'' said Rae, who added any images taken outside pre-arranged moments are shunned by British papers.

One member of the media, from one of the three Canadian television crews named by the palace yesterday, pointed out that camera crews here in Whistler are doing other stories surrounding the visit, and wondered what they are supposed to do if the princes just happen to walk by.

``If they do appear by chance, people are very nice . . . they put down their cameras and go away,'' said the palace spokesperson.

Yesterday's intrusion by the television crews had reporters navel-gazing once again. About 320 media representatives have been accredited for the six-day visit, and close to 100 of them are in Whistler. For the vast majority who are abiding by the rules, there wasn't much else to do yesterday but interview other reporters and camera operators.

Robert Hardman, a columnist and royal correspondent for Britain's Daily Telegraph newspaper, had other things on his mind. The Canadian visit is seen by royal watchers as a coming out of sorts for the two young princes, he said.

``We don't get to see them together that often, and what we saw in Vancouver was a first, where the three of them acted as a team doing official duties.''

But the big story for the British press has been the thousands of Canadian teenage girls who swooned and cried at the sight of Prince William.

``From now on, in any event where these boys are in the public, it means there is going to be a media army, not to mention a public army as well,'' said Hardman.

So far, Whistler residents and the thousands of holiday skiers on the slopes seem oblivious to the royal guests - a far cry from the reception that greeted snowboarder Ross Rebagliati when he returned home with Olympic gold.