Daniel Gooch used the Star class, more precisely the “North Star” locomotive developed by Robert Stephenson, as a basis for developing a new broad-gauge express locomotive. He stayed with the 2-2-2 wheel arrangement and a driving wheel diameter of seven feet, but installed a larger boiler.

In the years 1840 to 1842, seven manufacturers made a total of 62 locomotives. The names of the locomotives did not follow a uniform scheme. In addition to names that began with “Fire”, there were also those that came from Greek mythology or from animals. From 1865 they were counted to the Priam class.

“Fire Fly” is said to have traveled the almost 31 miles from Twyford to London Paddington in 1840 at an average of 50 mph, which was a record at the time. Later, the locomotives were fitted with new cylinders that were 16 by 20 inches instead of 15 by 18 inches. The withdrawals took place between 1864 and 1879. A working replica of “Fire Fly” was completed in 2005.