Jersey royals is a brand name for the potato" international kidney"
. It can only be sold as Jersey royals if it is grown on Jersey.
to get that real taste of jersey royals you need their soil and feed them with seaweed.
Jersey soil is very sandy and free draining so if you have a heavy clay soil results will not be the same. Also the climate is generally quite different to UK mainland, overall warmer & milder. Plenty of seaweed available at source too.