The tourists, on the 14th day of a three-week tour, were on their way from Sabi Sabi game reserve, near the Kruger National park, to Pretoria, winding through a switchback pass in the eastern Drakensburg Mountains.
There were skidmarks on the road half a mile from the crash scene, according to Tinus Joubert, a local who was one of the first on the scene.
Fanus van Eck, chief of public safety in nearby Lydenburg, who was also quickly on the scene, said the accident happened where the road makes a sharp turn. "The brakes of the bus failed. The bus overturned and the roof tore off," he said. "From where the bus left the road it overturned, rolled and some of the passengers flew out. It seemed like the bus rolled over some of the passengers."
There were 37 people on the bus, including the driver, who survived, and three tour guides. The holiday was booked through Thomas Cook, while the bus belonged to the Springbok Atlas bus company, based in Cape Town.
The first television pictures of the incident showed the roof of the coach had been ripped off and rescue workers were seen carrying away many of the dead on stretchers.
A local journalist, Quentus Loots, said he had spoken to the the driver. "The driver had nearly managed to get out of the pass. We understand that his brakes had failed but if only he had managed to keep it under control for another few minutes he could have used one of the rest areas," Mr Loots said.
The rest areas are gravel-filled lay-bys which can be used to slow down runaway vehicles. Mr Loots said he came across a scene of "utter carnage" when he arrived. "We found a group booking form for a hotel for the night before, everything was covered in blood and diesel."
Staff at Lydenburg's small hospital said the driver was among seven victims still being treated there yesterday evening. Three more had been moved to the provincial capital of Nelspruit to receive intensive care. According to a rescue driver at the hospital, George Viljoen, the coach driver had broken bones in his hip and thigh but was able to talk.
Mandla Mahlangu, a senior police official, said 23 people died at the scene and the rest in hospital. "It's a mess, we are busy trying to clear the scene at the moment," he said.
The 35-mile long Long Tom Pass where the accident happened is a tourist attraction in its own right as the site of the last formal engagement between British and Boer troops in the Anglo-Boer war, almost 100 years ago. Then the same switchbacks that contributed to yesterday's tragedy allowed retreating Boer gunners to rain the last of the shells from their "Long Tom" heavy artillery pieces on British columns advancing up the pass.
South Africa's Transport Minister, Dullah Omar, expressed his condolences to the families of the victims and said the South African government would conduct a high-level investigation into the accident and make sure it was conducted to the satisfaction of the British Government.
He said Springbok Atlas had an excellent safety record up until now and tourists in general travelling on the roads in South Africa were safe. While this is the fifth South African bus crash this month, it is the first to involve foreign tourists.
Thomas Cook's general manager, Simon Laxton, said the company was sending a five-strong team of engineers, legal advisers and customer service representatives to provide support for survivors and to mount their own investigation into the accident.
The company has also set up an emergency hotline for worried relatives, 01733 417502.
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