Looks like we have a lot of British "nationalists" leavers downvoting everything here.
I mean, you comment is basically a fact: Brexit implied losing Schengen, it was part of it from day 0. Putting back Gibraltar in Schengen is a defeat for Brexit supporters.
EDIT: not Schengen, sorry, although I'm pretty sure I just used my national (European) ID to go to London many many years ago and not my passport.