What do you mean by authority? There's always been immigrants in Britain. Saxons, Danes, Norwegians (Vikings), even blacks,army and navy, although they were not identified as such in any records usually, and other people from the Mediterranean, and further east. Never any problem.
Too many for assimilation now perhaps.
Royal Bucks Militia 1790. To be seen in Buckingham, Aylesbury, Chesham, Beaconsfield, Slough etc.