Martin Underwood wrote:
I know that initially the changover of letter occurred on 1 January, until
they realised that this caused a rush in car orders just as garages and
distributors were returning from their Christmas holidays. I believe the
change to August-to-July "years" was in 1966. So does that mean that:

A, B, C ran from Jan-Dec
D ran from Jan-Jul
E onwards ran from Aug-Jul

making D a short "year"?

More or less, but E was the short year, and the changeover in 67.

London's use of A suffixes didn't extend to buses - there were never
any A reg Routemasters until some got re-registered when the original
numbers got valuable.

But Aldershot and District did have A reg buses, and I don't think
they were registered in London.

Anyone know why Northern Ireland never adopted any of the year-letter
formats. I'd have thought the army would have wanted a unified system so
that British soldiers' private cars were not quite so obviously different
from Northern Irish residents' cars, so as to lessen the chance of them
being IRA targets.

I think it was for compatibility with the rest of Ireland, though it
continued after the Republic went over to a new system in the late
'80s. I think they use the same system as the rest of the UK now.

Disclaimer: I didn't look any of the above up.

Colin McKenzie