After a hiatus of 22 months since Christmas 2019, steam returned to the main line on Saturday 2nd October 2021 with a series of test trains between Whitehead, Carrickfergus and Magheramorne Loop. Due to engineering works at Whiteabbey, the Larne line was closed to service trains and the RPSI had the line to itself. These were non-public trains to test that all was well with locomotive (No.131) and carriages. Also, there was a reassessment of the drivers and firemen. Whitehead - Carrickfergus; LE: Carrickfergus - Greenisland & return; Carrickfergus - Magheramorne & return; LE: Carrickfergus - Greenisland & return; Carrickfergus - Whitehead - Carrickfergus; LE: Carrickfergus - Greenisland & return; Carrickfergus - Magheramorne - Whitehead (NIR) - Whitehead (RPSI).