It's been on mind - was driving behind a 3-series (E90) [u]facelifted[/u] (as it had the new rear lights and different shape wing mirrors) and the plate was of the usual format:

xx52 xxx where x is a letter
[url="http://en.wikipedia.org/wiki/Vehicle_registration_plates_of_the_United_Kingdom"]http://en.wikipedia.org/wiki/Vehicle_regis..._United_Kingdom[/url]

The THING is this means the plate was registered between September 2002 and before March 2003 but the facelifted E90 came out in September 2008 so the earliest plate could be a 58 one.

P.S. Do you know why the letters were S, T, V... i.e. missed out U? I can understand Z was omitted and the new style system started with 51 as Z could be mistaken for 2?

I always thought you cant make a car look younger than it is but by all means make it look older...

correct
you can put a reg on that is older but not newer


letters not used on the old prefix system were U, Q, O, I and Z
probably because they were too much like other digits
although Q plates were used for unknown aged vehicles

apparently U was missed out as it was too similar to V

As already said, you can make a car look older, just not newer. My sis has an M reg plate on her 56 plate car.......