This week Volkswagen has taken a significant (but far from final) step in drawing a line under the Dieselgate scandal, accepting a $4.3 billion fine, agreeing to plead guilty to criminal charges and accepting six executives must face federal charges.

But along with this plea bargain has come a number of lurid admissions that lay bare at least some of the depths VW employees sunk to in order to create and then try to hide the now infamous cheat software behind its emissions defeat devices.

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The full depth of analysis of VW’s signed agreement is best credited to the BBC’s Theo Leggett, whose full work you can read here. In brief, it highlights how:

- the plan to cheat emissions legislation was born in 2006, when VW supervisors realised they couldn’t meet targets for an engine set to be launched in 2007.

- the cheat device was then based on a system developed by VW's subsidiary Audi, but which engineers stressed should "absolutely not be used" in the US.

- immediately, engineers on the project "raised objections to the propriety of the defeat device".