I just done a search on the TFL "Fare Finder" page for Ruislip
(London Underground) to Hackney Central ( London Overground ). It
came out with the following results :

=========================================

Ruislip - Hackney Central

Oyster single fare
£1.80 Monday to Friday from 0700 and before 1900*
£1.00 At all other times including public holidays.
------------------------------------------------
Cash single fare
£3.00 At any time.
=========================================


So in theory a return journey can cost you as little as £2.00 outside
the hours of 0700 - 1900.

The fare pricing suggests that the route to be used cannot traverse
through Zone 1.
The obvious route is if you go via Finchley Rd Tube and then change at
Finchley Rd + Frognal but you will have to touch out at Finchley Road
and touch in at Finchley Rd + Frognal and hence will be charged for
two journeys and the total fare will be more than the £1.00 / £1.80
listed above.
If according to the above I only pay £1.00 / £1.80 for the journey, it
means I have to use a route which involves touching in at Ruislip,
touching out at Hackney , no touching out / in at immediate stations
and I MUST NOT travel through zone 1. Changing at Finchley Rd and
Finchley Road + Frognal is out of the question as I will have to touch
out and in again and get charged for two journeys. So for which route
is this £1.80 / £1.00 ticket valid ? Obviously I cannot go into
Central London ( ZONE 1) and then up to Highbury + Islington to
change for London Overground. I am trying to think of a route which
would involve :

1. Not exiting exiting / touching out and then entering / touching in
at immediate stations en route.

2. The provision to change trains at a London Overground station which
has a LU interchange and does not require me to travel through zone 1
to reach it !

Any suggestions for this route ??? The TFL journey planner suggests
the Finchley Rd, changing at Finchley Rd + Frognal route but then I
will get charged twice and the fare will be more than £1.80 / £1.00.

Cheers,

UC