Since the beginning of the railways, shunting services have been provided by older locomotives or by others designed for the purpose. This is the case with locomotives such as CP 1184, from the series which became known as ‘Sentinels’. Manufactured in Portugal by SOREFAME, under licence from Sentinel Works and with a Rolls Royce engine, they entered service in 1966/67. The aim was to replace old steam locomotives and provide auxiliary and shunting services.
They were small locomotives, but hardy and with low maintenance costs. They also performed other services, such as hauling short passenger trains on the Seixal and Montijo branches and various shunting services. These locomotives have been phased out of service.