Millions of rail passengers can now buy cheaper "advance" tickets on the day of departure, the Rail Delivery Group (RDG) has announced.
Until now, advance fares have generally only been available up until midnight on the day before.
Eight train operators are offering the service, claiming that the cheaper tickets can be bought as little as 10 minutes before the train leaves.
But advance fares are for a limited number of seats and often sell out.
When they are available, they can offer substantial savings.
For example, a single fare on the 10:03 from London to Birmingham for 5 July would have cost £52 if bought online on the day of travel.
The same fare bought eight weeks in advance currently costs just £11.
Advance tickets can potentially be bought on the day with CrossCounty, Grand Central, Greater Anglia, Northern, Transpennine Express, Virgin Trains East Coast, Virgin West Coast and Caledonian Sleeper.
They are not being offered on Arriva Trains Wales, South West Trains, Southern, Southeastern, ScotRail or First Great Western.
Customers of all long-distance services can now see online how many fares are left at cheaper prices.
Last year 27% of all long-distance rail fares were bought as advance tickets. They can be purchased either online or at ticket offices.
