"Paul Scott" gurgled happily, sounding
much like they were saying:

I saw a lorry delivering at Victoria yesterday to the Cornish Pasty
Co. The lorry reg began GN09. Now, I don't really care, because I
really like those pasties, but is GN a west country plate?

G's the mnemonic for Garden of England. Kent, Sussex, Hants.

Not quite.

G is Kent and Sussex (approximately) issued by the Maidstone and
Brighton area offices,

All Hants area registrations start H, from the Portsmouth area office.

Ah, yes. You're right.