Directly after his appointment as superintendent of the Lancashire & Yorkshire, William Barton Wright designed the class 25 as a standard goods locomotive. Between 1876 and 1887, different commercial manufacturers and the LYR's own Miles Platting workshops produced a total of 280 of these locomotives also called “Ironclads”. The first 72 had a smaller boiler than the remaining 208.

Between 1891 and 1900, 230 were rebuilt to class 23 saddle tank locomotives. At the LMS, the non-rebuilt locomotives were classed in power class 2F. Withdrawals commenced in 1930, but 23 managed to survive into BR ownership. The last ones were withdrawn in 1959. The only non-rebuilt locomotive that was preserved is BR 52044, former LYR 957 and now running on the Keighley & Worth Valley Railway. Class 23 No. 752 is now running on the East Lancashire Railway, carrying the fictitious BR No. 51456.