AN OXFORDSHIRE man has delved into what are believed to be unexplored caves hundreds of metres beneath Montenegro.

Mark Sims, 24, from Rowstock near Didcot, was part of a team believed to be the first people ever to shine light on an underground river which fell down a 250ft drop into an enormous chamber.

Mr Sims, who attended King Alfred’s school in Wantage, said: “Being the first people ever to see such incredible places is a feeling that is hard to put into words.

“The excitement of going around a corner and disappearing into the blackness, not knowing what’s there, is absolutely indescribable.”

He joined 16 students from York University’s Cave and Pothole Club on the expedition, but said it was not all plain sailing.

Mr Sims said that at one point, to get through a gap in a wall, team members had to take off their harnesses and squeeze through a tiny hole – on the other side of which was a steep drop.

He said: “I don’t think anyone isn’t scared at that point. Fear is quite a major thing.

“You like to think you are just walking around these huge places taking in the moment, but in reality there is a lot of concern.

“You don’t know when it is suddenly going to drop down 300 feet. It is also very awe inspiring.”

After the cave exploration, the team – which included geologists – presented a survey at the British Cave Research Association’s Hidden Earth conference held in Leek, Staffordshire.

Their adventures won them second place in the conference’s annual survey competition. Mr Sims, who is studying for a PhD in chemistry at York, said: “The potential for big caves in the area is huge since the hydrology suggests that a depth of 1.5km is possible, deep enough to be in the top 10 deepest caves in the world.”

Exploration of these caves is hard work, given low temperatures and the effort required.

The team also had a five-hour walk between their camp site and the nearest road.

Their efforts were rewarded as they managed to get 300 metres below the surface before running out of equipment and time.

During the two-week expedition, the team explored the caves beneath Montenegro’s Durmitor mountain range.

The trip was the society’s third to the region.

Mr Sims, who hopes to return next year, was among a group of explorers who discovered the entrance to the cave system last year.