From Rail Staff Travel http://www.atoc.org/rst/Updates_&_Reminders.asp

PRIVILEGE TICKETS ON OYSTER 'PAY AS YOU GO'

From 3 July 2006, safeguarded active and retired staff and their
dependants who hold a valid Staff Travel Card (STC) will be afforded
the option of participating at privilege rates (on London Underground
[LU], Docklands Light Railway [DLR] and National Rail services which
accept Oyster pay as you go) in the 'Pay as you go' Oyster
arrangement. As staff may know, the Oyster concept enables travellers
to pay for travel in advance by the addition of value to a smart
card.

The existing arrangements whereby LU/DLR privilege tickets for
individual journeys can be purchased before travel at LU Booking
Offices will remain.

The 'Pay as you go' Oyster arrangement is for leisure use only. Those
who travel on LU services to get to and from work (or dependants who
travel to an educational establishment) will still need to purchase an
appropriate Privilege Season Ticket. (Remember: Travelcard Seasons are
NOT available at privilege discount rates)

Transport for London is extending 'Pay as you go' Oyster to staff to
make it more convenient for those who make regular LU/DLR trips. The
benefits are two-fold; travel is cheaper (being based on the public
Oyster single fares which are cheaper than cash fares) and the need to
regularly queue at Booking Offices is eliminated.

Just ask for a Priv Day Ticket at the Ticket Office.

Richard Thomas