Considering the Jag was originally a trainer design I always thought its ability to go supersonic wasn't bad.
Haven't done a recent search, but I believe the Jag may have had its roots in the Breguet 121, which ISTR was a potential bidder for the NATO light-fighter competition (Sabre replacement?) that was sort-of won by the Fiat G91. Sort-of, in that only the Germans, Italians and Portugese ever bought them. As usual, facts are probably all over the shop - DuckDuckGo is your friend (never touch G00gle meself...)