A British woman who was the sole survivor of a flash flood in Thailand that killed eight people described last night how she saw her fiancé being washed to his death after he saved her life.

Helena Carroll, 21, from Solihull, was exploring caves in Khao Sok National Park 400 miles south of Bangkok with a group of tourists when heavy rainfall caused water to surge through the complex.

She said that John Cullen, 24, had pulled her to safety and then tried to go for help. He and five other tourists were killed, including a Swiss couple with two young daughters and a ten-year-old German boy. The two Thai guides who accompanied the party also drowned.

Miss Carroll, who was trapped for 16 hours before being rescued, said that the party had taken a two-hour boat trip to the Tham Nam Thalu cave complex, which they expected to take an hour to explore.

She said: “When we got in, it was amazing. We saw lots of bats and spiders in our torchlight but then, when I guess we had got halfway through the cave, I heard this sudden roar. I looked behind and saw this rush of water coming towards us. John and I started climbing. The first thing we saw was the tour guide and a ten-year-old German boy being dragged away, then the Swiss couple and their two lovely girls.

“As we climbed I lost my grip and slipped down, but John grabbed me and pulled me up. We kept climbing higher and found a ledge. We were all alone in the dark. We could not see anything as all the torches had gone.”

She said that Mr Cullen had decided to try to seek help, but was overcome by the waters. “John said, ‘If we stay here we are going to die’. But I said we should stay. At least we were safe where we were. But he decided that he would get into the current and flow with it. He thought the current would take him out, then he could bring help to rescue me.

“He slipped into the water and that’s the last I saw of him. He let go and he was just gone. I was alone in the dark. All I could see was insects that light up like fireflies, and hear the rumbling of the water. I sat there shivering all night. I had no idea what the time was.

“Then all of a sudden I saw a bright light. It was the light of a torch and so I started shouting, ‘Help, help — I’m over here.’ When I got out I was told that many people had died.”

The couple, both from the Midlands town, were a month into a year-long trip around the world. They had saved money for a deposit on a house but decided instead to spend it on a “dream holiday”.

They had travelled to the Khao Sok National Park, where tigers still roam what is described as the oldest rainforest in the world. It is also home to hornbills and rare plants.

It is not the first time that a tourist has been killed at the caves: a German woman drowned five years ago.

Thai police named the dead as Benno Fischer, 49, and Stalder Fischer, 48, both Swiss, and their daughters Ambarea, 17, and Sarah, 15. The German child was Eddie Gaempe. His mother did not take the trip because she was feeling unwell.

Thirayudh Mungapaisn, the deputy park chief, said: “We have issued warnings to tourists and put up signs about the dangers of visiting the cave during the rainy season.”

Last night the bereaved families began arranging for those who had died to be repatriated.

Miss Carroll, who works for the industrial training company Empower, said: “They took me to a place which was being used in a mortuary. I saw John’s body in a box next to one of the beautiful little Swiss girls. It was awful. John is a big man. He is 14 stone and everybody was remarking how big he was.

“I can’t believe my John is gone. One minute I was in what I thought was the most beautiful place in the world. The next thing, there is death all around me.”

Mr Cullen worked for his family’s insulation business but harboured hopes of becoming a full-time golf coach. His mother, Val, was understood to be away on holiday and last night did not yet know of her son’s death. Mr Cullen’s father, also John, died 18 months ago.

An inquiry into the incident began last night, with reports that national park officials had warned the guides not to continue the tour because of heavy downpours. Chalermsak Wanichsombat, the director-general of Thailand’s national park department, travelled to the southern province to lead the official investigation.

Speaking outside the family home, Miss Carroll’s father, John, said that his daughter was heartbroken. Mr Carroll said: “Helena had known John since they were at school together and they had been going out for almost four years. John was a smashing lad, clever, with good business acumen, and he looked after my daughter so well.”

Fatal attraction

— Thailand is the most deadly destination for British holidaymakers, according to the Foreign and Commonwealth Office

— It said that the figures, for April 2005 to March 2006 and released in British Behaviour Abroad, showed that “although Brits are getting more adventurous with their travels, they are not doing enough preparation before they go”

— Spain, which attracts 14 million Britons a year, tops almost every category for holidaymakers in peril. But when the figures are adjusted to show the proportion of visitors affected, Thailand is the most dangerous

— The 381,000 Britons who travelled to Thailand between 2005 and 2006 were nearly five times more likely to die than those visiting the second deadliest destination — India. Some 224 Britons died in Thailand

— British visitors to the country were also 50 per cent more likely to be taken to hospital in Thailand than in second-placed Greece. The latest figures show that 233 were taken to hospital

— Almost 900 Britons required serious assistance from a consulate in Thailand. That figure equates to 24 for every 10,000 visitors, double the rate for Australia

— Travel agents say that the problems are a result of cheap flights and under-prepared travellers

Times Recommends

• Thousands of Tamils dying in 'welfare camp'
• Jackson 'rebuilt his nose before he died'
• Renewed Iran protests crushed by militia