After a few months in service with the “Rocket”, Stephenson used the experiences to develop an improved successor. Since the placement of the cylinders of the predecessor was unfavorable for the running characteristics, the driving axle was moved to the rear and the cylinders were installed horizontally in front of the driving axle and inside the frame. It was probably the first locomotive with this arrangement, which later became the standard.

This arrangement not only improved the running characteristics, but also allowed the cylinders to be mounted inside the smokebox, thereby reducing losses from condensation. Also new was a steam dome, with which dryer steam could be extracted from the boiler. In addition, the front and rear buffers and couplers were roughly in the places where they are today.

On November 23, 1830, it was able to prove its performances by completing the 31 miles from Liverpool to Manchester in about an hour. The prototype was followed by six more by Stephenson and three made by Fenton, Murray and Jackson to the same design.

In the years that followed, many locomotives were built in several countries based on the “Planet” pattern, so that the 2-2-0 wheel arrangement was later named after it. The Liverpool & Manchester alone got 16 of them. The original “Planet” was first modernized in 1833 and retired in 1840. A replica that was built in 1992 was used regularly until 2017.