McDonald played the role of Helena Ravenclaw, AKA the Grey Lady, in Harry Potter and the Deathly Hallows – Part 2, who tells ‘The Boy Who Lived’ where to find the Ravenclaw Diadem.
Viewers have been taken to Twitter after putting the dots together and their minds are ‘blown’.
One person wrote: “Just worked out that Line of Duty’s Jo Davidson is Helena Ravenclaw and my work for the rest of the week is already done.”
“When you realise DCI Jo Davidson is also the ghost Helena Ravenclaw in Harry Potter and the Deathly Hallows,” wrote another.
A third penned: “I was today years old when I realised DCI Jo Davidson from Line of Duty is also the ghost of Helena Ravenclaw from Harry Potter!”
She replaced Nina Young who portrayed the character in Harry Potter and the Philosopher’s Stone and Harry Potter and the Chamber of Secrets.
Originally, she was asked to play Nymphadora Tonks in Harry Potter and the Order of the Phoenix. However, the role ended up going to Natalia Tena.
The 45-year-old has been appearing in films since she got her big break in the 1996 cult film Trainspotting.
Since then, she’s gone on to star in Nanny McPhee, Gosford Park, and Intermission.
For her role in the 2007 film No Country For Old Men, she was nominated for the BAFTA Award for Best Actress.
Line of Duty fans are currently loving her portrayal of ‘bent copper’ Jo Davidson on the hit crime drama.
One person wrote on Twitter: “Kelly Macdonald is absolutely terrific in #LineOfDuty.”
Another added: “Kelly Macdonald is brilliant as Jo Davidson. When she blows it’s going to be monumental.”
It’s unclear if she will return for Series 7, but we hope she does!
Featured Image Credit: BBC