Simplify the following text for a Grade 12 native English-speaking person.
Original: National Express East Coast is the name under which the train operating company NXEC Trains Ltd operates the InterCity East Coast rail franchise , which includes services in England and Scotland along the East Coast Main Line .
Simplified: National Express East Coast was a train operating company in the United Kingdom , running high speed passenger services on the East Coast Main Line between London and Scotland , as part of the East Coast passenger franchise .