Forms of tenses Past tense group
You use the simple past to express the idea that an action started and finished in the past or to list a series of completed actions in the past.
I left the hotel and went to the tube.
You use the past progressive to talk about a process that took place in the past, to indicate that a longer background action in the past was interrupted or to list a series of processes that took place in the past.
It was raining, I was waiting, then someone tapped on my shoulder.
You use the past perfect simple to talk about actions that were completed in the past already. It expresses the idea that something occurred before another action in the past.
London had grown immensely.
You use the past perfect progressive to show that a process started in the past and continued up until another time in the past.
Engineers had been planning an underground for many years.