In message , at 14:02:01 on Sat, 14 May
2016, tim... remarked:
The TfL site is astonishingly opaque regarding what cars are allowed
or not. They can't even be bothered to install a query based on
numberplate.

It appears to say that Euro 6 diesel cars must be less than 5years
old, but doesn't mention any of the former Euro ratings.

NO

What it is saying is that vehicles of this age are guaranteed to be
Euro 6 compliant (because that is the date that manufactures were
required to meet E6).

Older vehicles may be compliant if their particular model met Euro 6
standards before the required date.

Euro 5(D) cars will never be compliant whatever their age

Like I said, astonishingly opaque. My V5 doesn't say what Euro-foo the
car is, and TfL can't be bothered to help. Wonkypedia doesn't say
either. After a lot of digging it appears to be Euro 4 (diesel).
--
Roland Perry