The government has invested £62 million in the London Midland network.
A fleet of new electric trains has been added to the route, which connects the capital, midlands and north-west, with the move getting started ahead of schedule.
The Department for Transport originally expected the fleet to come into service in December, only for some of the trains to start running on Sunday (October 6th).
Busy morning services to and from London Euston will benefit from the extra capacity in particular, with trains between the station and Northampton, Bletchley and Tring already receiving hundreds of additional seats.
The remainder of the fleet will be introduced in December, in time for London Midland's new winter timetable.
Managing director of the company Patrick Verwer said the new fleet will make a "real difference" for people commuting into London. He also revealed it will allow the company to add more services to the Cross City line between Birmingham and Redditch, which is the busiest commuter route in the West Midlands.
The new fleet of trains are built by Siemens and feature plug sockets in standard class, on-board litter bins and two-plus-two seating.
Rail minister Clair Perry commented: "As part of our long-term economic plan, we are investing record amounts in transforming the rail network, providing more seats, more trains and better journeys for millions of passengers.
"Over the next five years, more than £38 billion will be invested in building a world-class railway across the country."
Ms Perry recently visited east London in order to see how work is progressing on the Canning Town to Victoria Dock tunnel, which is part of the Crossrail project. The scheme is the biggest infrastructure development in Europe and when completed will connect much of London and the surrounding area.
Running from Reading in the west to Shenfield in the east, the project will boost the capital's rail capacity by ten per cent.
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