Barry Salter wrote:

Perfectly correct, as there is no obvious way of travelling between the
stations in question without passing through Zone 1, and £1.50 is the
Oyster Single fare for a journey in Zone 1.

Notting Hill Gate is in an odd position zonewise.

Is Notting Hill Gate to Heathrow treated as Z1-6 or Z2-6? How about
Notting Hill Gate to Acton Town?

If they're treated as Z2-6, am I breaking any rules if I travel via
Earl's Court rather than Ealing Broadway? And if they're treated as
Z1-6 by default, is there any way to prove to the system that I traveled
via Ealing Broadway (e.g., touch an Oyster pad at Ealing Broadway) so
I'm charged the lower fare?
--
David of Broadway
New York, NY, USA