Pride
I don't own Law & Order: UK.
She enjoys being a DI. Growing up in a household where her beloved father was a police officer, she had always aimed to make him proud of her. It took many years but she finally made the rank of detective inspector.
Natalie visits him several times a year and talks to him at least twice a week on the telephone. He often is a touchstone for her when she and her 'boys', as she calls her detective sergeants, are in the middle of investigating a difficult case.
Though she does not like working the long hours, sifting through the facts of the often unsavoury cases, she wants to make the world a better place from her two sons. She wants to get rid of the disagreeable elements in society but it is hard work, taking her away from her children. Now that they are older, they understand, but when they were younger it was difficult. They couldn't accept the fact that their mummy wasn't going to be able to make it to a school play, or make it home for dinner. But now that they are sixteen and thirteen, they realise that their mother's work is important and they are proud of her, as proud of her as she is of them.
It's always a matter of pride.