Photographers got more than they bargained for when they tried to cross the guarded barriers of the derelict St John's hospital in Chelmsford.
Within minutes the Essex Police helicopter was in the sky tracking their movements, and officers and police dogs had them surrounded.
After a hospital security guard was attacked by a lead thief in April last year, security has been beefed up in a bid to stop tramps, metal thieves and the underground movement of 'urban photographers' who take pictures of empty buildings and share them online.
The men, who post their pictures on an online forum 28dayslater.co.uk, would only give their online usernames.
"We were warned that Chelmsford had the police base here and were tough on crime," said one man, who wanted to be known as Troglodyte, and had travelled from Hertfordshire.
The 26-year-old added: "Luckily they let us go because they knew we were not thieves or causing any harm, we are just part of a community forum.
"I have been doing this type of work for about six years now, as people are really interested in buildings they do not usually get to see.
"I have been caught once before by the police but usually it is fine and I can get into most places.
"What we want to emphasise though is that we never break into anywhere, we take only photos and leave only footsteps.
"It has definitely been an eventful experience in Chelmsford and I do not think we will be coming back."
The eerie corridors of the hospital are still filled with redundant medical equipment and files, and even a white board in the old children's ward is covered in poignant messages.
Troglodyte's 25-year-old friend, whose online username is Yeah-Mick, added: "I have been stopped by the police in Harold Wood before when I tried to enter an old morgue.
"I saw the police officers had weapons when they found us in St John's Hospital, so we were lucky.
"But we actually did not do anything, we slipped under the gate, and one of the windows was open in the hospital so we did not break anything.
"We took a few photos but the police still let us go with a warning."
Urban photographers have amassed an anthology of pictures of the hospital since it shut in November 2010, and have also photographed the derelict Marconi factory in New Street, which has been targeted by thieves, drug addicts and the homeless.
PC Martin Spensley, who was on the scene, said: "We caught them within two minutes of us arriving on site.
"As soon as they saw us they put their hands in the air and we knew they were not typical criminals, because we saw they had cameras. Our main concern is that they were metal thieves, which is why we take these acts of trespassing so seriously.
"Criminals always say they were not doing anything when we catch them, but this time it was genuine.
"We gave them words of caution and then asked them to leave the premises."
