The fares leaflet also includes something completely new that's
interesting and doesn't seem to have been publicised. Currently,
through tickets are available between Tube/DLR and NR, but they are
charged at the same price as buying a separate ticket for each leg.
However, the PDF introduces a new concept of "Tube/DLR - Train fares":

"Tube/DLR - Train fares cover through journeys
between the Tube/DLR and National Rail and
are the maximum that you will pay for a single
journey in the London zonal area."

The tickets are zonal singles (with a return costing twice the single
fare). Although they are more expensive than Tube singles (and
*considerably* more expensive than pre-pay fares), for the first time,
there are singles available which are "blind" as to whether the
journey covers Tube/DLR, NR, or both. Is this the first step towards
the harmonisation of rail fares across modes in London, and the
ubiquitous validity of pre-pay?

There is a note saying: "and are the *maximum* that you will pay for a
single journey in the London zonal area"

What does this mean? Are they priced at the highest possible rail fare
they could find in order to make them valid to any rail destination in the
respective zones?

The implication is for some routes these will represent bad value if the
rail companies fare (+ the tube journey) is much less than the combined
ticket.

Is there any mechanism to protect the customer from buying the more
expensive ticket?