On Thu, 21 Jun 2007 05:11:37 -0700, Sam wrote:

If you're travelling Off-Peak and you have a Network Railcard, it's
often cheaper to buy a One-Day Travelcard than use PAYG Oyster, even
with the daily capping.

Only at weekends - the £10 weekday minimum fare prevents you from
buying a Z1-6 ODTC during the week.