1739hrs - We're going to wrap up here. It was an interesting session, with some sharp questioning from MPs and a stern defence from Willis.
The key revelations appear to be:
Around 400,000 UK cars need injector replacement at worst; the extra tank that's required in some American vehicles won't be needed here.
There are increasingly wide calls for the official test procedure to be modernised sooner rather than later.
VW's defeat device did influence the NOx emissions of cars on UK roads - which means it was operational during at least some NEDC EU tests.
1733hrs - Interesting to see MPs criticising Willis, since his departure from the meeting, for continually prefixing his answers with the phrase, "I'm not an engineer…"
Yet when McLoughlin is asked if the Department for Transport has done any physical checks on vehicles, he replies, "I'm going to risk your wrath here by saying this, but I'm not an engineer…".
Laughter breaks out in the room, from the panel and the witness desk; clearly it's funny if an MP says that line, but not a car company boss.
1731hrs - McLoughlin says there are some car companies who have not yet responded to letters asking them to reassure the Government that they don't have defeat devices fitted to any of their vehicles.
He says they've got until the end of the month to respond. But he adds, "These are reputable companies, in the main. We have an enviable record on car production in this country, and on engine production."
1722hrs - Willis and Hawes have now left the room. The Minister for Transport Patrick McLoughlin is now answering questions.
He says he was first aware of the dieselgate problem on the weekend of 18th September. He says he believes VW has behaved "in an appalling way".
1720hrs - Hawes adds that the forthcoming real-world emissions standards will help to rebuild confidence.
"We will ensure that this real-world driving emissions regulation will be delivering real-world emissions betterment," he says, "and the investment in those technologies will continue to improve. Customers can be assured that the vehicles they buy will remain fit for purpose and will deliver the reliability, safety and emissions performance they expect."
1718hrs - Mike Hawes says he's not sure if the motor industry has been really hurt by the scandal.
"It would be premature to say that the reputation of the motor industry has been damaged by this," he says. "The industry is doing a lot to address air quality issues, and we will continue to make significant investments to make sure those issues are addressed. This issue around regulation and its impact in the real world is one that is being addressed and has the full support of the industry."
1715hrs - Willis is asked if there was a high-level corporate decision to install the cheat device or if he thinks it was down to a few software engineers.
"That debate and discussion is pure conjecture," he says. "I have no idea. I would be guessing. I find it implausible that senior people in the company would have known these issues with the testing regime."
1714hrs - Willis is asked if VW will compensate the Government on any money that was saved in tax by cheat device-equipped vehicles.
"I'm not sure there's any clear evidence that the CO2 emissions on these cars is different in the real world," he replies. "We can have a discussion further down the line. The British taxpayer should not be out of pocket. If necessary we will have the meeting with HMRC."