In message , at 13:00:57 on Sun, 8 Sep 2019,
Graeme Wall remarked:

*I had an idea they were already considering as far as the M25.

There's a certain amount of resistance to that from communities
inside the M25 that do not consider themselves part of London.

There's resistance from a lot of people! (See also colloquial
conflation of GLA/M25).

The difference being that the Mayor's writ does not extend as far as
peoples perceptions of London.

Those perceptions including "The GLA", "Inside the M25", "Patrolled by
the Met Police", "with 070 phone numbers", "served by TfL bus routes"
and no doubt other metrics as well.

So it's a bit fuzzy round the edge, but "M25" is a reasonable and
commonly used approximation.
--
Roland Perry