An Oxford University academic has been condemned by police and rail officials for glorifying a night-time climb to the top of the Forth Bridge – an experience he described as like “riding a dragon”.

Dr Bradley Garrett staged the climb last year while studying a subculture of people who explore off-limits urban spaces, known as “place hacking”.

In a forthcoming book, Explore Everything: Place-Hacking the City, he details how he and several others sneaked on to the Forth Bridge and climbed across its full 2,500-metre span. At one point, the group feared they might fall when it started to rain and the 110m-high bridge’s beams began to get slippery.

Speaking to The Independent, he claimed his research, which was carried out while he was at Royal Holloway University of London, had helped him get his current job at Oxford University partly because “they respected the lengths to which I went to understand this culture”. However, a spokesman for Oxford denied that the university had endorsed his fieldwork.

However, British Transport Police and Network Rail took a rather different view. “Trespassing on any part of the railway infrastructure is illegal and extremely dangerous. Trespassers put themselves, rail staff and passengers in danger and British Transport Police works closely with Network Rail to ensure that anyone indulging in this activity is prosecuted,” the police said in a statement.

A spokesman for Network Rail told the Scotland on Sunday it was “very disappointing that a publisher is trying to profit from something as hazardous and illegal as trespassing on the railway”. “The Forth Bridge is a busy structure, which is in use 24 hours a day, and attempting to climb it illegally is as stupid as it is dangerous. We will always seek to prosecute anyone found trespassing on our infrastructure,” the spokesman added. However, it is understood that police are unlikely to seek to prosecute Dr Garrett.

In his book, Dr Garrett wrote that as a sleeper train crossed the bridge the “structure shook and screeched” and “I felt like I was riding a dragon”. On the way down, he said his heart was “pumping furiously”.

“A small list to the right and I would fall 110 metres into the Firth,” he said. “I knew that 63 men had died building this bridge, and I couldn’t help but imagine their ghostly bodies plummeting through space and the feeling of helplessness I would experience if one of my friends fell.”

It then began to rain, and they feared they might fall off. “Despite our better judgment, some of us start standing up on the beams, crawling on all fours like bonobos, speeding down the last cantilever structure before the beams got too wet to hold on to,” he wrote.

Dr Garrett said on Sunday that while he could be prosecuted for going on to the railway, there was a six-month statute of limitations – and he had waited until this had expired before speaking out. He railed against Britain’s health and safety culture for trying to prevent people from taking risks, saying that Germans were allowed more freedom to do dangerous things if they signed a waiver.

He said he was not encouraging others to do the same but added that some people were “a little bit rebellious” or liked to “push up against edges and boundaries”. “Everyone should do that at the level they are comfortable with.” he added.

Dr Garrett has previously scaled the Shard skyscraper and Battersea Power Station in London, and also visited secret communities of people who live in subterranean drains in Las Vegas and the catacombs beneath Paris. He said part of the attraction to illicit urban exploration was the potential for life-threatening situations.

“I’ve had a number of occasions where things began to get a bit tricky and you think to yourself, ‘I’m not going to make it through this’,” he said. “You become hyper-conscious of the present and you really attuned to what’s happening around you because you know any lapse of your concentration may mean that you die.”

And climbing structures like the Forth Bridge illicitly was also part of the appeal. “It’s an incredible feeling to have traversed the whole bridge … in the middle of the night, four people, and no one ever knew that we were up there,” he added.

Place hacking: highlights

On climbing the Shard while it was still being built: “It was boring. You couldn’t see anything,” he said. “You’re just sitting there in the clouds. It feels like you are coming in on a plane. It’s just not that interesting.”

On sneaking on to a crane in Aldgate, east London, at night: “There was an incredible view from that place. I wrote some of my book sitting in that crane.”

Arriving at a former Soviet military base near Potsdam in Germany on the recommendation of an unknown Twitter user: “It was in the middle of a forest and we thought ‘We’re either going to get murdered or it’s someone having a laugh’, so we drove out there... We had to know!”