On a disastrous three-man caving party in Slaughter Stream Cave in the Forest of Dean, he had plunged 15 feet off a ledge to land under the cascade. A colleague had also fallen, and lay in a crumpled heap nearby. The third man had gone for help but had got lost in the pitch-black labyrinth of tunnels, and returned having been unable to find his way out. "I thought the hypothermia was going to kill me," recalls Ian. Grimly, they all waited.
Specialised help was already massing its ranks. When the trio failed to meet friends at a pub, the alarm was raised and Gloucestershire Cave Rescue Group scrambled into action. Around 40 volunteers, all experienced cavers, arrived at the cave entrance in the early hours of the morning. Ropes, ladders and a human network were set up. Rescuers were equipped with neoprene exposure bags to swaddle casualties in, and "little dragons" - specially heated oxygen to infuse warmth into the body.
The UK's 16 cave rescue organisations are called to 60 such incidents each year. Rescuers battle their way in darkness, often without radio contact, through cave systems that can run to 30 miles. But they don't rescue only cavers. Often they recover animals that have fallen down shafts (one team boasted the rescue of a duck last year), and have helped the police to recover hidden murder weapons.
At a conference of cave rescue teams, hosted by the South Wales Cave Rescue Organisation last month, I joined hardened cavers as they practised new techniques - from containing hypothermia to using explosives in rescue. Deep underground, cave divers mounted an exercise using a stretcher specially designed for immersion in submerged tunnels.
Pete Allwright is secretary of both the British Cave Rescue Council and the country's busiest team, the Cave Rescue Organisation in the Yorkshire Dales, which responds to 25 per cent of all call-outs in the UK. "Underground, you can forget all about ambulance call-out times," he explains. "Unlike Mountain Rescue, who can sometimes just fly people out with a helicopter, we have to retrace the casualties' steps to take them out. The operation can take many hours."
Sergeant Chris Pappin, based at Ingleton, North Yorkshire, is the liaison officer between the police and the Cave Rescue Organisation (CRO), to which all 999 calls for emergencies in caves are referred. "On paper, the police have overall control of an operation, but in practice it is all down to the CRO," he says. "We really just provide a supportive role for them."
As volunteers know to their cost, rescue work carries an emotional price. In August this year Christine Bleakley, a 24-year-old student, fell to her death negotiating the Quaking Pot at nearby Ingleborough. It is listed as a grade 5 pot, and the most dangerous in Britain. "The name really does make rescuers quake in their boots," says Pete Allwright.
Yet, thanks to rescue organisations, fatalities are relatively few. "If someone dies it affects you badly, especially if you are on the rescue team," says Constable Andy Watson, who was involved in the operation to try to save Christine. "Cavers are a close community, and her death was felt by everyone."
Yet accidents tend not to deter cavers. Certainly Ian Jeffries' fall hasn't dampened his enthusiasm. He'll be back down again as soon as his leg is mended.
Deep in the bowels of the Ogof Ffynnon Ddu black limestone caves in Wales, a glimmer of light pierces the darkness. Within seconds a team of muddy rescuers appears, rapidly hauling a stretcher up an underground stream. There is no real casualty, just a volunteer tied to the frame for the purposes of training. It is dank, chilly and a long way to the surface.
Why do people go caving? "You can be the first to find a passage nobody has been in before," explains a mud-bespattered caver. "It is the challenge of the unknown." And he beams.