GWR Pannier Tank 9600 worked a Banbury to Princes Risborough charter on July 3rd, and another GWR Pannier, 9466, is currently doing two weekends on the Looe branch top and tailed with a class 37.
The reason small steam locos aren’t regularly used for railtours is because they lack the power to maintain the higher speeds that running on Network Rail demands whilst coping with the long and heavy carriage rakes that are necessary to ensure there are enough punters on board to cover the costs of the tour. They also only have a short range between taking on coal and water, which would require frequent stops on anything other than a short distance charter service.
9466 and 9600 are the only two tank engines registered for use on the mainline, and also the only two steam locos smaller than a 2-6-0 tender engine registered. The 2-6-0 tender locos get around a fair bit (The K1 and K4, and BR Standard 4 76079): I've seen 62005 working a Whitby to Fort William charter with the stock for the Jacobite, which is definitely a long distance working, so the smaller tender engines are obviosuly very capable machines.
