A family have described their shock at realising a 30ft-deep sinkhole had opened up in the driveway and swallowed their car - but also their relief that nobody was hurt.

Liz and Phil Conran's teenage daughter discovered the 15ft-wide crater at the family home in Main Road, Walter's Ash, High Wycombe, Buckinghamshire, early yesterday morning.

Mrs Conran said her daughter, 19-year-old Zoe Smith, went into hysterics upon discovering her prized Volkswagen Lupo had disappeared into the ground.

Explaining what happened Mrs Conran said: "My daughter went to go and let her horses out because she was going off somewhere for the day and she had to drive up there, and she got herself all ready, got to the door, and saw her car wasn't there.

"She thought that was a bit weird, of course it was still fairly dark outside, so she went round to the kitchen window and then she saw the crater and just started screaming.

"We just kind of took it from there really.

"We had no idea whether the car was actually in the hole or not, we couldn't get close enough to have a look right down to the bottom, it's about 30 feet deep.

"The car is on its side, its full of soil and she certainly, we don't think, would have got out of it had she been in it, had she driven in and it had happened."

Mrs Conran, a 51-year-old school bursar, said the relief that nothing had happened to her daughter was the overwhelming emotion, while the rest was "just an annoyance".

"What could have happened to Zoe is so awful that we just feel so lucky that we're all okay, that actually we've not really had much chance to worry about who's going to pay for it and what's going to have to be done," she said.

However Zoe, a sales assistant, was "absolutely gutted" because she had been so proud of her car, Mrs Conran said.

She said the family, including her 59-year-old husband Phil who works as an environmental consultant, were stunned at the size of the crater that had appeared in the driveway of their home, where they have lived for the last nine and a half years.

"The actual size of it is what I think has taken us most by surprise," she said.

"It's just swallowed the car whole. The car has managed to rotate and turn, it's on its side but its also facing the opposite way from where it was parked.

"So just the sheer size of it, and obviously what could have happened, and of course we're wondering what else is going on in the area."

She went on: "It's one of those natural things that has happened, probably been made worse by the fact that they've mined in the area in the past but whether or not that's got anything to do with it we don't know."

The family stayed with neighbours last night after being advised to stay away from the house and are waiting for a insurance company representative to come out later today to assess whether they can remain in the house tonight.

When the hole first appeared, which Mrs Conran said they think might have happened around 6.15am, they did not know what to do because nobody had been hurt and they suspected the car was down the hole, so rang the local police.

"They said, 'oh we don't think there's anything we can do, it's going to be a building insurance job and a car insurance job', so we got off the phone from them and thought 'oh yeah, you know they're probably right there's not much they can do' but they obviously changed their mind because fairly quickly we had two Panda cars and a fire engine parking up outside and cordoning it all off.

"Once they decided that there really wasn't anything they could do, they weren't going to be able to get the car out or anything, I think people were just coming to have a look because they just couldn't believe that this had happened."

Mrs Conran said there were no signs of the sinkhole starting to appear - no cracks in the drive or in the house, no dip in the ground - and they did not hear it as it happened.

She said an employee from the building services department at the local council had told them it would not be expected to hear anything because sinkholes usually occur slowly as the ground simply slips away.

Also, the family were still in bed on the opposite side of the house with the doors and windows closed at around 6am, Mrs Conran said.

The next step was to find out if their property was safe to stay in, she said, and then tackle the issue of insurance.

"There's the usual when you have subsidence or anything like that, we've already been told there's a £1000 excess, so we'll have to swallow that," she said.

"Then obviously they'll have to make good but we're not sure what that will entail at all and how far down it goes.

"Obviously we can see earth 30ft down and the car but what we can't see beyond that and how stable it is under the house, so that's going to be a bit of a drama."

Firefighters were called to the family home at 8.32am yesterday.

A Buckinghamshire Fire and Rescue Service spokesman said: "Firefighters were called to a sinkhole (30ft deep, 15ft diameter) which swallowed a parked car in the driveway of a house in Main Road, Walter's Ash.

"Firefighters placed a cordon around it and gave safety advice.

"The incident was handed over to building control at Wycombe District Council. Firefighters were at the scene for about an hour."

Paul Beetham, a lecturer in civil engineering at Nottingham Trent University, said: "High Wycombe is a chalk area, and chalk has properties quite different to other types of rock. Areas underlain by chalk may contain natural voids or caves which formed over many thousands of years as groundwater passed through and dissolved the chalk.

"High Wycombe is also an area that has been mined historically for chalk and, occasionally, mining areas can have access shafts which were not capped off correctly, leading to loose material overlaying these voids.

"While such cavities may remain intact below ground for hundreds of years, very rarely the sudden collapse of the material may occur, perhaps when disturbed by extreme rainfall or a recent change in land use."

Mr Beetham said this type of occurrence is rare in the UK and there are "well-mapped" areas where chalk or limestone underlie the ground, such as the Peak District.

He said around 5% of the surface area of the UK could potentially have such rock underneath, but not all will have conditions that could promote sinkholes.

In late December witnesses reported a sinkhole in the village of Foolow, in the Peak District, which was said to have measured around 160ft wide.

"We're talking about just a small area of the UK, 5% say, that may be underlying limestone or chalk. Then within that small percentage local conditions or past use may have promoted this type of feature.

"So from the point of view of, 'Are there large cities or towns suddenly all at risk?' - the answer is no more than they always were, and it is rare situations can crop up."

Sinkholes around the world have made headlines in the last few years.

In February last year 37-year-old Jeff Bush was killed when his detached bungalow in Tampa, Florida, disappeared into a huge hole as he slept.

A sinkhole reported to be nearly 200ft wide in China's Sichuan province swallowed around a dozen buildings in December but no one was seriously injured.

Mr Beetham said sinkholes on that type of scale would not be seen in the UK.

"Around the world, Florida for example, the type of environment promotes itself to a big cave feature in that type of area and the gaping, monstrous, hundreds of metres types of caverns are not a feature of the UK."