On this specific case, you need to read the story to get past the headline - looks like you have to have been there to tell whether this was reasonable or not (and I appreciate I've altered the story by selective quoting...).
The stunned crew of an air ambulance were ordered off the estate of a billionaire sheik after landing there to rescue an unconscious horse rider
.
The sheik is fifth on Forbes magazine’s global ‘rich list’ with a £9billon fortune. His head of security confirmed the helicopter had landed, saying: ‘It just plonked down outside the house, landing on private ground without permission, and that was the issue. Aircraft can’t just fly in like that. I understand it was an emergency, but they should have notified us. We have people working in the grounds, including gardeners, and if they have protective earphones on they can’t hear anything. It could have landed on top of someone, or there could have been other aircraft coming into the estate – we do have a landing area here. One guard was relaying back to me what was going on as I was in the control room. I told the guard to tell them to contact me direct, but before we could sort it out they just took off again.
We don’t have a problem with the air ambulance landing here or cutting the fence. They’ve done it before, but we do need to be notified first. Sheik Al Maktoum wasn’t here at the time, but even so it sparks a panic if an aircraft suddenly appears on your lawn.’
An air ambulance spokeswoman said: ‘We landed on Sheik Al Maktoum’s estate and were prepared to cut the fence and guards did approach the crew. But at that point we received a radio message saying that the patient wasn’t as badly injured as we thought. The medical team had a discussion with the guards and a decision was taken to move the helicopter.’
On the general point, I would have assumed the law would allow access to save life/prevent serious injury (rights of the injured override the life of the land owner), but can anybody clarify?