One took over many East Anglia train services in April

National Express has merged services from the old Anglia, Great Eastern and West Anglia routes under the name One.

But the Office of Fair Trading wants to ensure the merger has not substantially lessened competition on long-distance rail and coach routes in the region.

The commission is expected to report its findings in November.

One provides services from Liverpool Street to Hertford, Cambridge, Peterborough, all of Essex and to Norwich and east coast resorts.

Fares on some One routes went up on Sunday with the introduction of the new summer timetable.