Past tenses

Until a few years ago, no one            [heard, have heard] of Harry Potter, the young wizard and hero of the children’s book Harry Potter and the Philosopher’s Stone

The writer, J K Rowling,              [was writing, wrote, have written] several stories and books, but this was the first book that was published

. She         [got, had got]                [travelled, had travelled, was travelling]the idea for the story of a wizard at magic school while she on a train to London

By the time the train             [had reached, was reached, reached] King’s Cross station, she              [has invented, invented, was invented] most of the characters

When the book was published in 1997, no one              [had imagined, imagined] it would be such a success, but it quickly            [became, had became, was became] a bestseller

While millions of young readers in many countries               [was enjoying, were enjoying, enjoyed] her first Harry Potter book, J K Rowling              [was thinking, thought, had thought] of ideas for the next book in this incredibly popular series.