If anyone is thinking of buying a diesel, then just bear in mind the press tends to bunch all of them together.
Emissions standard Applied to new passenger car approvals from Applied to all new registrations from
Euro 1 1 July 1992 31 December 1992
Euro 2 1 January 1996 1 January 1997
Euro 3 1 January 2000 1 January 2001
Euro 4 1 January 2005 1 January 2006
Euro 5 1 September 2009 1 January 2011
Euro 6 1 September 2014 1 September 2015
If you buy a car which is older than September 2015, double check the log book, to see if it's Euro 5 or Euro 6 compliant. Certain manufacturers such as BMW started putting Euro 6 engines in as early as March 2014.
The T(oxicity) charge is being implemented in Central London this October and will apply to all Euro4 vehicles. Euro 5 vehicles are expected to be impacted in 2019/2020 and may go out as far as the North and South circular roads.
Other cities are considering the same sort of restrictions to pre Euro 6 vehicles