The transition period for Brexit will end in a few weeks and after it Belgium will lose access to much of the area it fishes in the North Sea if there is no deal. The UK and the European Union resumed their talks on Thursday on a post-Brexit trade deal, with fisheries among several sensitive issues still blocking the way to an agreement.
Belgium may resort to a charter granted by the Britain's king Charles II in 1666 to retain fishing rights in Britain’s coastal waters if they fail to agree a trade deal. It gives 50 Flemish fishing boats access to British waters for perpetuity. It states it's an "eternal right" so according to a Belgian minister it is still valid.
The "Fisheries Privilege" document is conserved at the States Archives of Belgium, in Bruges. They are our founding member and content provider and you can find their documents here: http://www.archivesportaleurope.net/directory/-/dir/ai/code/BE-A0513
Read more in this Reuters article: https://www.reuters.com/article/uk-britain-eu-belgium-privilege/belgium-dusts-off-1666-charter-for-post-brexit-fishing-rights-idUKKBN27722D
Pictured: A view of the original document, conserved at the State Archives of Belgium, in Bruges. Source: Wikipedia.