Diesel units took over next day, with faster trains and a more frequent service.

For a few moments the two rattle along side by side until the faster train pulls away.

On a quad-track line, faster trains can overtake slower ones.

What are the restrictions on using existing track to run faster trains?

This arrangement also allows the station to serve as a point where slow trains can be passed by faster trains.

Having more trains, however, does not mean having faster trains.

The third route forms the second Main Line run by the company, with faster trains available from the next stations east and west.

It is no good having faster trains when you still have to wait ages for a train to the nearest fast -train station.

The trains will be gradually retired to make way for a new generation of even faster trains.

The Government's plan will inject huge amounts into the economy and deliver faster trains - eventually.