The NER Class Y was Wilson Wordsell's last design for the NER during his tenure as CME before he retired in 1910.  He was succeeded as CME for the North Eastern Railway by Vincent Raven who had twenty of these 3-cylinder engines built at Darlington Locomotive Works between October 1910 and June of 1911.

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They were put to work on short haul trips from Collieries to the Staithes releasing the same number of tender engines from these duties.  However by 1923 most of the class had been redeployed on hump shunting duties at marshalling yards throughout the North Eastern Area where their power was useful.

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As built all the class were fitted with the diagram 55 boiler.  Originally They were saturated steam engines but they began to be fitted with the Schmidt super-heater in 1917.  Not all the class were super-heated, one carried a diagram 55 saturated boiler until withdrawal.  By 1943 diagram 63B boilers began to be fitted to the class.  This was unusual because the Diagram 63B boiler was of a smaller diameter.  Fifteen locos' were rebuilt, fourteen with the diagram 63B boiler and one with a diagram 63C boiler. These re-boilered engines became Part 1 of the class A7.

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All the class were fitted with steam brakes and 3-link couplings when new but one of the class, No. 1179 got a vacuum ejector and steam heating pipes at both ends for trials on passenger trains on the Newcastle to Blackhill services.  This came to nothing and the equipment was removed in 1943.

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Withdrawals started in 1951 with 9789.  This engine never received a BR number.  Withdrawals continued each year from then until 1957 with the exception of 1953.  The last three to go were retired in December1957 making class A7 extinct.