It’s a doorway to darkness, an opening cut into the side of a hill. It leads to a long, low tunnel. I have to crouch down to avoid hitting my head. All we can hear is the crunch of our feet on the ground. All we can see are the spots of light from our torches.

We walk down into the darkness. My guide, Andrew Watson, points his torch at a hole in the tunnel wall. It’s about 2ft high. Andrew used to be a coal miner and tells me the 2ft-high tunnel is typical of the ones he used to have to crawl down when he worked in the mines. I tell him it sounds hellish. He shrugs. You get used to it, he says.

We walk a little further on. At the end of the tunnel is a T-junction. There’s water dripping on us from the roof. It’s soggy underfoot. Our torches light up the beams above. Andrew says he can take people to this area of the tunnel and recreate almost every dangerous situation you can think of: fire, heat, gas, explosion, you name it. It doesn’t look like it, but this dark, wet tunnel is a kind of classroom.

The pupils who come to the classroom are the men and women of the Mines Rescue Service. Officially known as MRS Training & Rescue, the service was established over 100 years ago to rescue miners from accidents, but it has since diversified and now trains rescuers to work in all kinds of dangerous and difficult situations: tunnels, wind turbines, high buildings – anywhere where someone could get into trouble and where effecting a rescue would be difficult. The tunnel we’re standing in is part of the service’s training centre in Crossgates in Fife.

Back up on the surface, the day’s training has already started. James Twigg, a 35-year-old paramedic, is standing at the bottom of a high metal structure and is being kitted out to climb to the top. James works for the Ambulance Service’s Special Operations Response Team and has come to Crossgates to prepare for some of the situations he might face. It could be an explosion in a power station; or someone hanging off some scaffolding; or someone trapped underground or high on a wind turbine (the training centre’s facilities include a replica of a turbine).

James says the prospect of working at the top of a wind turbine or somewhere else high up is new for him, although the trickiest part so far, he says, has been training in water. “The idea is that no matter where our patient is,” he says, “we should be able to get to them rather than have the patient brought to us. We definitely take risks, but the more training you do, the more confident you feel.”

Kristofer Sweeney and Aaron Lindsay feel the same way. Kristofer, 27, and Aaron, 26, are the latest trainees to be taken on by MRS and this week they’ve been getting used to the kind of kit they’ll have to wear in some of the trickiest rescue situations: thick bodysuit, heavy backpack fitted with oxygen tank, and a helmet connected by a tube to the oxygen supply.

“It’s amazing how quick you get comfortable with it,” says Aaron. “And when you’re dragging a stretcher, you forget it’s on your back.” This week, Aaron and Kristofer have been going into smoke-filled containers to look for dummy casualties and getting them out as quick as they can.

Aaron says it’s been a tough experience, but he’s also realised that the risk and danger is carefully managed. “If you’re not willing to put yourself at risk, there’s probably no point in getting into this line of work,” he says, “but they talk to us about risk all the time. Everything is risk, risk, risk. We learn to prioritise the casualty and each other and you could be involved in any kind of situation which is why the training is so extensive. You have your stand-by man and nine times out of ten it’s the most experienced guy and you’re going to trust him with your life.”

Aaron is talking about men like Andrew Watson, my guide in the tunnel. Mr Watson, 64, who is the service’s specialist technical advisor, grew up in New Cumnock in Ayrshire and was a face worker in the mines by the time he was 18. Before long, he became interested in the rescue side of the job and joined the Mines Rescue Service in the 1970s. At the time, the service had 26 rescue centres up and down the UK, including four in Scotland. “It was a dangerous job and people died regularly,” he says. “The figure in the 1950s was a fatality every three days.”

A lot has changed since then of course. The coal mining industry has disappeared from the UK, but it’s still very active elsewhere in the world and Mr Watson’s expertise is in demand in other areas too. He helps trains the service’s new generation of rescuers like Kristofer and Aaron, and rescuers in other organisations such as James. He also does a lot of work in Colombia and other countries advising mining companies on how to improve their safety standards. And over the years, he and his colleagues have been involved in many search and rescue operations, including some of Scotland’s most notorious accidents and disasters.

One of the operations that particularly sticks in Mr Watson’s mind happened in Glasgow in June 1981. Two floors of a tenement building in Shettleston were being demolished when suddenly the whole lot collapsed into the barber shop on the ground floor. The demolition men, James Mulligan and Dennis Ashcroft, were rescued, but the barber, Joe Eusebi, and his customer, John Wilson, were trapped in the rubble and sadly could not be saved.

Mr Watson remembers that terrible day vividly because he was the first rescuer to make his way into the rubble to reach the men’s bodies. “The reason the fire and rescue service wanted us there was to shore up the collapsed building and to move several tons of rubble to access the casualties,” he says. “I remember getting to the barber’s customer very quickly, then it taking a long time to actually release the body. It was a sad day.”

Mr Watson also talks about some of the other operations in which the rescue service has been involved. One of the most famous is the Knockshinnoch disaster in New Cumnock in 1950 in which 129 miners were trapped underground by an in-rush of peat and earth. Thirteen of the miners could not be saved, but 116 were led to safety. In 2004, MRS teams also attended the Stockline Factory explosion in Glasgow in which nine people were killed and 33 injured. The emergency services, including MRS, worked for days to rescue the survivors.

MRS operations manager, Errol Parrish, was one of those on the scene at Stockline. “We received a call a few hours after the explosion,” he says. “The fire and rescue service had recovered casualties, but other people were still trapped in a very unstable structure. The priority was to save life and recover the trapped people while at the same securing the safety of the rescuers.

“When MRS arrived, we were met by the sight of dozens of firefighters moving tons of debris by hand, which was taking a long time. We set up supports to secure what was remaining of the structure and then created pathways into the areas where casualties had been identified. Over three days, we helped in the rescue of a number of casualties, but also the recovery of others who had sadly lost their lives.”

The staff at mines rescue service also particularly remember another distressing case in Glasgow in 2002. John Storrie, an 18-year-old student, was swept into a hole that had opened up in Riddrie graveyard in Glasgow during heavy rain and when MRS arrived at the scene, it was hoped James might have survived in an air hole. Two diggers were used to excavate a trench before rescuers in wetsuits were lowered into the tunnel to search the water inch by inch. Sadly, James’s body was found after five days.

Thirteen men from the service were involved in the operation and Jim Malko, who was assistant manager of Crossgates at the time, said it was one of the service’s most dangerous cases.

''There was a lot of water, flooded to the roof in places,'' he said. “There was debris that had been washed in by the rain and we had to dig our way through silt to reach the casualty.''

Inspector Les Gray, of Strathclyde Police who co-ordinated the rescue, also praised MRS. ''The Mines Rescue Service was superb,” he said. “They are a fantastic bunch of guys and never stopped working – unless it became unsafe. They never gave up hope.”

Stories like that one – sometimes with a happy ending, sometimes not – have been Andrew Watson’s life work and he is still highly motivated by a desire to help.

“In my days,” he says, “you wanted to be the guy that helped and that’s typical of the mining community. My son Andrew was born in a mines rescue station and it’s in-built: you want to help. It gets into the blood.

"In my entire career, I’ve only ever been uncomfortable once, in Colombia, when they took me down what was supposed to be one of their safest mines and I thought, I have to go back out. I’ve been in explosions, I’ve been in fires, and I’ve always felt in control of this because I understand exactly what’s happening and the effect of what I do.”

Mr Watson says it is this understanding of managed risk that’s central to the work they do at the training centre in Crossgates. He tells me about the methane explosion at the Cardowan colliery in Lanarkshire in 1982 in which 41 men were injured, which he and his colleagues recreated in the tunnels at Crossgates.

“The explosion at Cardowan was a slow methane explosion,” he says, “The guys could actually sit and watch the flame coming towards them. They had nowhere to go. They had to get into the side the best they could and turn their back to the flame. But the flame was going to go over them. We recreated that here at the training centre and the trainees could see smoke coming towards them – we lost about 25 per cent of our rescue men at that point. A few of them didn’t come back, because they didn’t like it.”

Mr Watson says this is one of the intentions of the training process at Crossgates, where his son Andrew is now deputy manager. “We are looking to see how they react,” says Mr Watson. “You’re putting them into a hard experience. You get a mixture of personalities: you have guys who will try and fix everything and make it worse. You have a debrief and tell them what they should have done. What we can do is get people to think the right way. These guys are here to take a risk, and they will take a risk to save lives, but it has to be an acceptable risk because there’s no point in them killing themselves. You have to weigh it up – if I have a good chance of saving life, I will take a risk. But if there’s not a good chance of saving life, then I’m not taking the risk.”

It’s that kind of experience that Andrew Watson is passing on to the young trainees such as Kristofer and Aaron. They start on a 12-month probation period during which the trainers look to see if they have what it takes. Some people get claustrophobic in the confined spaces, some don’t like the breathing apparatus, others struggle to follow orders and think they know best. “We’re looking at their traits,” says Andrew Watson Jnr, “and some people realise after a while that they don’t have those traits.”

Kristofer and Aaron are still in the early stages of the training, and after five weeks or so will be assigned to one of the rescue teams that are based all over the UK, at nuclear power stations, in mines, and construction sites and so on.

It’s obvious straight away that both Kristofer and Aaron have a strong sense of personal responsibility and commitment, although Kristofer tells me some people were surprised when he told them about his new job.

“Some of my friends were surprised I was going to work for Mines Rescue,” he says, “because you don’t really hear about it – obviously, there were the Chilean miners rescue, that was a big event, but other than that, you don’t hear much.”

For Kristofer though, who used to be a construction worker, the training has been a revelation. “It’s better than being stuck in an office all day,” he says.

Aaron feels the same way and already has a strong commitment to the service. “You’ve got to care,” he says, “it’s not about coming in and just getting a pay cheque.” It’s a philosophy that Andrew Watson has believed in his whole career.

We head back towards the tunnels where Mr Watson tells me more about his days as a miner. He remembers leaving school when he was 15 and his dad taking him to Lugar in Ayrshire in search of a job in the mines. “I never even got out of the car. My dad came out and said, ‘you start on Monday’. I did three months training on the surface and then I was underground and I was a face worker by the time I was 18.”

In those days, he says, the face workers were the risk takers – they would get the coal at any cost – and health and safety was something other people worried about. Now, thank God, it has changed entirely.

“That culture completely changed for the better,” he says, “and the culture is you do it correctly, and you do it productively, but you’re safe. We want somebody who is willing to take the correct level of risk.” And it’s worked: a mines rescuer hasn’t been killed in action since the 1940s.

Mr Watson’s job, and his vocation, is to pass those lessons on to the new rescuers who regularly come to Crossgates. In the last 18 months alone, 14 new recruits have been trained here and they’re now part of teams based all over the UK. The main focus, always, is to prevent accidents happening, but they will also be ready when something does go wrong. It could be at the top of wind turbine. It could be in the rubble and dust of a collapsed building. Or it could be where it all started for this extraordinary emergency service: deep underground.