The Parkgate Waggon Co. (Parkgate) (plaintiff) owned and operated a business that rented out wagons to customers. Parkgate entered into two long-term rental contracts with Lea & Co. (Lea) (defendant). Lea agreed to rent a total of 100 wagons from Parkgate for a period of seven years. In exchange, Parkgate agreed to perform all required maintenance and repairs on the wagons. A few years into the rental agreement, Parkgate sold its interest in the wagon business to The British Waggon Co. (Waggon) (plaintiff). Waggon agreed to assume all of Parkgate’s maintenance and repair obligations. Waggon performed these services successfully for some time. When Lea learned of the assignment, it sought to terminate the contract with Parkgate based on Parkgate’s assignment of its maintenance and repair duties to Waggon. Waggon and Parkgate brought suit to enforce the rental agreement with Lea.