The NER Class P1 (LNER Class J25) was a class of 0-6-0steam locomotives of the North Eastern Railway. Class P1 was a development of Class P, having a boiler four inches longer, and a firebox six inches longer. To accommodate these, the wheelbase was increased by nine inches. The cylinder stroke was also increased by two inches.
A total of 120 was built at the North Eastern Railway's locomotive workshops at both Gateshead and Darlington, between 1898 and 1902, in six batches of 20. Their numbers were 1961-2000, 2031–80, 2126-42 with the remainder scattered between 25 and 1743.
During World War II, 40 locomotives were loaned to the Great Western Railway (GWR). The first transfers to the GWR occurred in October 1939, and the last was not returned to the LNER until December 1946.
The general LNER renumbering scheme was prepared in 1943, and at that time, 85 locomotives of the J25 class remained: these were allotted 5645-5729, being renumbered during 1946, apart from six which had been withdrawn in the interim.