If we try to find the difference between the above statements , we will see that the difference appears to be very minute. To understand it better , let’s go to the root of the sentence.
If we carefully examine the sentences, we will see that the first sentence belongs to the simple past tense and second one is a part of past perfect tense. Now let’s see when we use past simple and when we require past perfect.
Simple past tense is used for all past actions which started in the past and ended in the past. Past perfect is used for the at of past only but after that some other past actions must happen. So past perfect is used when the series of actions happen. Quite often it is used for the first action and for the rest actions past simple is used
Let’s take an example
When I reached the house of my friend, he had left for his office.
Here we have two actions.
One is reaching house and another is leaving for office
Now out of these actions leaving for office happened first and reaching home happened later. For the first action we have used past perfect and for the next one we have used simple past. Some more examples are.
I sold my car because it had become very old.
As my friend had promised, he helped me a lot.
When the cops reached the spot, the thieves had escaped.
She was shocked to see her result. She had never got so less in all subjects.