For new suburban lines in London, James Sterling developed a tank locomotive with a 0-4-4T wheel arrangement, which was based on the G&SWR Class 1, which he had developed earlier. The 34 locomotives that were built first still had a bogie that could not be moved sideways, while the bogie of all the others could be moved sideways. Some of the locomotives had a lower chimney and a condenser for use in tunnels. After the transition to the SE&CR, 55 locomotives were rebuilt to class Q1. The last machines were gone by 1930. 