The remainder was built between 1844 and 1850 by the Chester and Holyhead Railway Company as the route of the Irish Mail services to Dublin.

So important was the line in the 19th and early 20th centuries to passenger, mail and freight traffic between Britain and Ireland that the world's first experimental and operational water troughs were installed at Mochdre, between Colwyn Bay and Llandudno Junction.

Their purpose was to enable steam engines (especially on the Irish Mail) to collect water without stopping.

A revised timetable has operated since December 2005 incorporating a new service to and from Cardiff Central every two hours.

[6] The Electrification Task Force said that the Chester to Crewe line was a Tier 2 priority for being electrified in the CP6 period (2019-2024).

[8][9] Class 221 units currently operate long-distance services to Holyhead from London Euston for Avanti West Coast.