How long did it take Holman Hunt to paint the picture of Jesus knocking at the door?

According to the Keble College website - the painting hangs in the Keble Chaple - Hunt began the picture when he was 21 years old, but it was not finished until he was 29.

One of the reasons it took so long was his desire to perfect the dawn. Hunt took the picture with him to the Middle East and found the perfect dawn outside Bethlehem.

When he was nearly 70 years old, he painted a life size replica which hangs in St Paul's Cathedral, London.