Evidently 1985 was the date of the "amnesty" I referred to earlier.
The trick (if it is a trick) would be proving this to French or German Customs.
Can anybody find some documents on the original UK Customs & Excise ruling on this? Even I can remember reading about it in the papers at the time, and that was a long time before I got into flying.
However, I wonder whether the French etc are obliged to consider a
UK Customs VAT amnesty? Surely they must do so under the VAT treaty; that is how certificates of free circulation worked. All EU Customs people hated the Danish ones (obtained as they were over 1 day of a Danish lawyer owning the plane, in return for a nice 4 figure sum
) but, according to a presentation to went to a few years ago by an aviation lawyer, they had no option but to honour them.