After the contruction of the P Class, the midland Great Western Railway decided that they needed a light tank and so in 1891 and 1893, a class of light tanks were delivered by Kitson & Co and Sharp Stewart. With their design and performance similar to the LBSCR Terriers, they earned the nickname, Irish Terriers. The purpose of the these tanks were as shunters in Dublin Broadstone as well as serving branch lines such as the Athboy, Achill and Clifden Branches. After 1924 and the creation of the Great Southern Railways, they managed to retain their MGWR identity till the late '20s when they were renumbered, names removed and painted in the standard GSR grey. During the GSR and later CIE, the engines received shorter chimneys and continued to work on the MGWR territory and often went beyond it, shunting in Broadstone, Westland Row, Galway, Limerick and working branches on the CBSCR Trimeologue Branch and the DSER Shillelagh Branch in 1932-1933. In the 1930s, three engines of the class were sent by road to the isolated Waterford & Tramore Railway and were rebuild with extended cabs for more coal capacity and modified footsteps. These engines stayed here till replaced by Diesel Railcars in the 50s where No.560 was then moved to the Fenit Branch to work the pier and was the last survivor in 1963.