The Great Western Railway Sun Class 2-2-2 broad gauge steam locomotives for passenger train work. This class was introduced into service between April 1840 and January 1842, and withdrawn between January 1864 and June 1879.A smaller-wheeled version of the Fire Fly Class for working trains on the hilly sections of line west of Swindon, they did not prove heavy enough for the task and were later altered to become 2-2-2T tank locomotives.