[2] In 2012, Transport for London announced its intention to procure a fleet of new, longer DMUs, as the Class 172 units then in service were unable to handle the passenger demand, causing overcrowding throughout the day.

[6] Since then the planned procurement was increased to 45 four-car EMUs, with the additional six units intended for the Watford DC Line.

[10] In April 2018, the Islington Gazette reported that the trains would be introduced three months later than scheduled due to delays in their testing.

[11] In June 2018, the Barking & Dagenham Post reported that the trains would be in service by November 2018, "almost 18 months later than planned".

[20] On 12 October 2021, the driver and a passenger were injured when an eight-car Class 710 train, headed by unit 710124, ran through the buffers at Enfield Town.

[23][24] He was subsequently convicted of endangering the safety of the railway and sentenced to sixteen weeks' imprisonment.