Henry Adams famously said that no American ever dies in the land of his birth. He wasn’t referring to migration; he simply meant that America changes.
I’ve lived in Britain, and no older Briton today is living in the land of his (yes, or her) birth. Forget “Upstairs-Downstairs,” that’s long gone. Today “A Clockwork Orange” better describes the country. The Home Secretary - in charge of security - wears a bullet-proof vest when walking in her own neighborhood.
The George Wallace third party run in 1968 was the beginning of that reaction. Richard Nixon paid attention to the shift away from permissive treatment of criminals. His appointees to the Supreme Court, while by no means conservative, were generally opposed to the anti-prosecutor and criminal rights bent of the Warren Court. Mike Dukakis' liberal tendencies with respect to pardons seriously hurt his 1988 Presidential campaign. Defeats of liberal jurists and politicians on law and order issues, such as with Jerry Brown in California in 1982, Rose Bird's recall in 1986 in the Golden State, and Mario Cuomo in New York in 1994, were major blows to the permissive approach to criminals. As for gun control, almost all ballot measures proposing greater regulations were defeated in the 1980s and 1990s. The hostile reaction to the Brady Bill by gunowners was a major reason for the Democratic rout in the 1994 elections.
The lessons of the 1980s and 1990s became clear to liberals. Promoting lenient treatment of criminals and supporting gun control were political suicide outside of hard core Democrat areas like big cities, college towns, and elite suburbs.
However, as you point out, things change. The fact that New Jersey recently abolished the death penalty may indicate the pendulum is turning back to permissiveness here.
The only way the crime situation in Britain will turn around is if the British public becomes sufficiently angry and demands tough sentences for convicted criminals and permit law abiding citizens to be armed once again.