it used only marginally more coal in working 300 ton trains than the K2s did with considerably lighter loads. The successful trials with No. 3441 led to five more being built. Apart from the prototype Loch Long all were named after Highland chieftains and grandees. Operations The K4s quickly endeared themselves to the Scottish crews and, apart from some heavily loaded summer trains, eliminated uneconomic double-heading over the West Highland. However, as with all Gresley 2-6-0s it could be a rough ride at speed, and a locomotive designed to climb was not suited to the flat straight stretches of the line into Glasgow Queen Street railway station, or the 8.5 miles stretch alongside Loch Eil. Ride induced vibration was a problem on these stretches, and the middle big-end bearing would require regular nut tightening, with the middle connecting rod dropping off on one occasion: this resulted in increased maintenance inspections. Crews began to prefer the LNER Class V4, but their lower power restricted their use and the K4s retained their pre-eminence on the West Highland line until the 1947 arrival of the first B1 4-6-0s, which replaced the K4s from Glasgow to Fort William. These were followed after nationalisation by an influx of Stanier 5MT 4-6-0s and the new K1s, that left the K4s increasingly confined to goods workings. During the 1950s, the K4s' sphere of operation enlarged and they began to appear at locations such as Edinburgh, Perth, Forfar, Ayr and Tweedmouth. In 1959 all were concentrated at Thornton in Junction depot in Fife and all were withdrawn in October 1961. Numbering In 1945 Edward Thompson rebuilt 3445 MacCailin Mor into the first LNER Thompson Class K1. LNER 1946 numbers 1993–6/8 and BR numbers 61993–6/8. Preservation One of the six strong class has survived into preservation, following the efforts of the late Viscount Garnock, who purchased No. 61994 The Great Marquess from British Rail (BR) and had the engine overhauled to working order. Based at Leeds No. 3442 undertook railtour work until forced into retirement by the ban imposed on steam working by BR in 1968. From 1972 No. 3442 was stored on the Severn Valley Railway (SVR) until 1980 when it was overhauled. In the mid 2000s, No. 3442 was bought by John Cameron and the locomotive left the SVR for overhaul at Crewe. Following the completion of its overhaul at Crewe it was returned to service on