Peter Francis, one of the oldest cave rescuers taking part, and who is responsible for the discovery of parts of the cave, called the incident "an unfortunate, chance accident".

"This incident is a one-off, although this is a world-class cave system. It's Himalayan by cave standards, it's a fairly safe area.

"You're more likely to be knocked down by a bus than this happening to you."

Paul Taylor, spokesman for South and Mid Wales Cave Rescue Team, said: "The alarm was raised at around 14:30 on Saturday afternoon, when a man who was with him alerted us that his partner had fallen.

"I don't actually know how many were in the group but there would've been more than two."

Rescuers have managed to find the man and put him on a stretcher, but it could take another 10 hours before he is lifted out.

Rescue teams have not yet revealed how far he fell or the extent of his injuries, but one rescuer said: "He's lucky to be with us. He's in a bad way."

It is the longest cave rescue ever undertaken in Wales, according to spokesman Paul Taylor.

He said the previous longest was 41 hours, and this one has already taken more than 48 hours.

Image source, Catherine Raine

These shots show the Ogof Ffynnon Ddu cave system which is part of the same area, but a different section to where the rescue is taking place.

The landscape shot is looking down the hill from the top entrance.

Image source, Catherine Raine

Image source, Catherine Raine

Image source, Catherine Raine

Underground controller Julian Carter has done two shifts in the past 10 hours, co-ordinating efforts.

While he described it as a "challenging rescue", he said conditions have been generally good with water levels low and the care of the casualty "exemplary".

As the third largest cave in Great Britain, he described its appeal: "It has three entrances, and you can traverse each entrance around this amazing landscape.

"Some of it is crawling, some horrible, other parts just fabulous, through the active streamways, around the remarkable landscape."

He also praised all the volunteers who have taken the day off work to help.

The caves where the rescue is taking place were discovered by the South Wales Caving Club in 1946, according to Natural Resources Wales, external, and feature underground streams and waterfalls.

They can only be accessed by cavers with a permit from the caving club.

The system is about 902ft (275m) deep at its deepest point.

The MP for Brecon and Radnorshire, Fay Jones, said her thoughts were with everyone involved.

BBC Wales reporter Rhys Williams gives an update on the cave rescue from the scene.

The injured man has been talking to his rescuers, a spokesman has said.

Paul Taylor said: "Caving is challenging in itself. Add into that the dimension of an injured casualty they have to move."

He said taking up a man on a stretcher was a difficult process, adding: "As far as I'm aware, he's been talking to his fellow cavers, who are now his rescuers."

There have been 242 people involved in the operation, the rescue team has said.

They also said the injured man is in Cwmdwr quarry cave, which is used as the entrance to Ffynnon Ddu section two.

This is what it looks like inside the cave where the rescue operation is taking place.

• A rescue operation is under way after a man fell hurt and himself while caving in the Brecon Beacons two days ago
• He fell while caving in the Ogof Ffynnon Ddu cave system near Penwyllt, Powys, on Saturday
• The man is being moved to a top cave entrance after being unable to get out himself due to his injuries
• At least eight rescue teams from across the UK are involved
• The cave is Britain's third longest

A YouTube video shows rescue practices with the South and Mid Wales Cave Rescue Team.

It was filmed in Ogof Ffynnon Ddu Two, in the Cwm Dwr entrance passages.

The video sheds light on how a rescue like today's could be carried out.

The injured man has been moved to the top of the cave as the rescue operation to get him out continues.

One Tribe TV filmed inside the Ogof Ffynnon Ddu cave network in 2016.

It was for a production called Extreme Wales with former rugby player and adventurer Richard Parks.

Image source, One Tribe TV/ BBC Cymru Wales

Image source, One Tribe TV/ BBC Cymru Wales

Image source, One Tribe TV/ BBC Cymru Wales

Some of the rescuers helping today were involved in the Thai cave rescue in 2018.

Divers in northern Thailand rescued 12 boys and their football coach from flooded caves, 17 days after they got trapped underground.

Their plight and the dangerous three-day operation to free them gripped the world's attention.

Image source, Getty Images

An update has been given on how teams have been working together in the rescue.

Paul Taylor, spokesman for the South and Mid Wales Cave Rescue team, said: "On Saturday, 6 November 2021, a male caver was undertaking a trip in the Ogof Ffynnon Ddu cave system and fell, resulting in some injuries that meant he could not exit under his own steam.

"A fellow caver notified the police and the South and Mid Wales Cave Rescue Team initiated a response.

"This incident is ongoing and involves cave rescuers from teams across the UK, Gloucestershire Cave Rescue Group, Midlands Cave Rescue Organisation, Derbyshire Cave Rescue Organisation, Mendip Cave Rescue, the South East Cave Rescue Organisation, the cave rescue organisation and the Upper Wharfedale Fell Rescue Association and other associated teams.

"The response to the incident has continued during the night and we are moving the casualty towards the top entrance of the cave, which is located upon the mountain and will be the point of exit."

The extent of the man's injuries are currently unknown.

Rhys Williams

The team here have radio communications with others involved in the operation.

Those at the cave entrance are talking to rescuers underground via something called “cave link”.

This is described by Paul Taylor, spokesman for the rescuers, as “black magic.”

In this system, text messages are sent through the rock without a need for cables.

Some of the cave rescuers here are internationally renowned, and some have travelled from as far as Upper Wharfedale in North Yorkshire.

Some of the people here helping with the effort were also involved with the Thai cave rescue in 2018.

Paul Taylor, the spokesman for South Wales Cave Rescue Team, said the casualty was being brought up from the cave.

"The response to the incident has continued during the night and we are moving the casualty towards the top entrance of the cave which is located up on the mountain and will be the point of exit," he said.