"TKD" wrote in message
. ..

Epping was only added to the TfL zone system recently (1998ish) -
previously, the stations on the Epping branch of the Central Line outside
of Greater London behaved like the Met stations beyond Moor Park do now.
The idea is to simplify life for Tube travellers (and for TfL
ticketing!). The stations around Hainault, many of which are also in
Essex, were in the zone stysem from the start to simplify life for
passengers going round the loop.

All of the stations on the Hainult loop are within walking distance of the
Greater
London boundary. The main reason for there inclusion was probably so a
journey
from Woodford to Hainault (both in London) would not be charged
excessively
because of passing briefly into Essex.

In fact, the only station on the Hainault loop outside Greater London is
Chigwell.

Grange Hill and Roding Valley are right on the boundary line.