There was a dark cloud hanging over the British Touring Car Championship paddock at Croft last weekend, and it wasn't just because of the temperamental North Yorkshire weather.

A serious accident in qualifying left three drivers in hospital, and two in an induced coma.

Motorbase Ford Focus driver Luke Davenport was the most seriously hurt and suffered multiple chest injuries, lung damage, a broken right leg, a broken pelvis, broken right arm and concussion.

He has been placed in a coma to help with his respiration, and has undergone several operations.

Eurotech Honda Civic Type R driver Jeff Smith has multiple chest injuries, extensive shoulder injuries and concussion. He was released from intensive care earlier this week and placed in a trauma unit.

Aron Taylor-Smith was also involved, and the MG man suffered concussion and a broken leg.

It happened because Davenport had gone off the circuit on his quick lap in qualifying.

As he rejoined the circuit at the 130mph Barcroft bend, a line was ripped off the oil cooler, dropping fluid all over the already-soaking circuit.

Eight other cars went off the track as a result of the accident, and several were significantly damaged.

ITV commentator and 1992 BTCC champion Tim Harvey acknowledges that the shunt was just a set of circumstances combining, and also says that the safety measures in the cars did an excellent job in the impact.

"We had a wet track, we had a car dump oil coming back on to the track and where it dumped oil was right at the turn-in point to the fastest corner on the track, with very little run off," he says.

"The drivers were obviously completely powerless to do anything about it.

"It is a bit like hitting black ice at 10mph. You can't control the car - let alone at speeds which are north of 100mph."

While the accident was unavoidable, the damage to the cars was huge. Most race cars are designed to withstand one big impact, but in this case two cars had two large hits.

Firstly, Andrew Jordan's WSR BMW 125i M Sport was in collision with Davenport's stricken car, before Smith then hit the driver's door at unabated speed.

Then, when Smith's already damaged car came to a rest on the grass on the outside of the circuit, Taylor-Smith's MG ploughed into the side of that too.

Once a car has been hit once, it weakens the structure. Any subsequent impacts are the ones that cause significant damage and, in this instance, injuries.

"The damage was also unfortunate because it involved a lot is side impacts, which are the worst impact that any touring car can have," adds Harvey.

"We are all mindful of what happened to Keith O'Dor many years ago [O'Dor, pictured below in his BTCC career, was killed by a side impact racing in the German STW Cup in 1995].

"You can't please everyone in terms of making the car safe. We could make the cars like a NASCAR with multiple steel tubes down the sides and the drivers climbing in and out through the windows, but that is not what these cars are. They are touring cars - that is not the essence of them.

"I think they stood up very well to the impact. The intrusion into the car was enormous on both Davenport and Smith's cars but fortunately the drivers do sit a long way towards the middle. They also sit behind the B-post.

"But these were enormous accidents and you can't legislate for that."

There was one area of concern in terms of the accident procedure: the speed at which the red flag was shown. It was 30 seconds from the time the first images of the accident were screened until the decision was taken to halt the session.

"If I was the clerk of the course with my finger on the red flag button, I would have pressed it as soon as I saw the first images because of where it was on the track and the nature of what was going on," says Harvey.

"Clearly cars were out of control - they don't go off at that point unless there is a serious problem.

"My first words on the commentary were: 'there must be oil on the track'. It was an instant red flag for me.

"I don't know all of the details of what happened, but 30 seconds does seem like a long time in terms of that accident."

Series director Alan Gow said that yellow flags before the incident were sufficient, but he wasn't sure that a red flag could have avoided the subsequent crashes after Davenport had gone off.

"I have no concerns," says Gow. "The yellow flags came out straight away, which means that the cars coming up knew that there was an incident.

"There were waved yellows, and you can see that on the on-board [footage] from cars involved in the incident.

"If a red flag had have come out, cars would have slowed down at the same pace. They don't stop immediately on the track when there is a red flag, so the outcome would probably have been the same."

Gow also heralded the strength of the NGTC-specification cars, which were fully introduced into the championship back in 2014 to replace the previous S2000 machines.

"If that was in a previous generation of car to that which we have now, the outcome would have been a lot worse and a lot of the teams involved in the accident have said that too," he says.

"In the NGTC cars that run in the BTCC now, we have put a lot more effort into moving the drivers further inward and there is more side protection. That played its part in protecting the drivers here."

Despite that, Gow says that both cars would be examined and the damage would be studied to see if there was any information that could be useful.

"We will be carrying out a full engineering investigation on the impact to the cars and see what can be learned," adds Gow. "The cars stood up fantastically well given the incredible violence involved.

"Clearly the strength of the integral crash protection did its job - but we never stop learning and never become complacent about safety."