A billion people tuned in to Diana's marriage to Prince Charles in July 1981.
Why was it such a big deal?
1981 was a difficult year. Loads of people lost their jobs when UK factories shut down.
The world was changing and Britain was losing out to countries who made better goods for less money.
Celebrating the wedding showed there were some things Britain could still do well.
Diana was at the centre of all this, she became an important figure of hope to many people.