Knight was in a relationship with Waterloo Road co-star Abby Mavers from 2013 to 2017.Knight started in West End Theatre with Deborah Warner's production of Euripides' Medea, (Queens Theatre, 2001), Knight is best known for playing Luke Smith, adoptive son of Sarah Jane Smith, in the first three series of The Sarah Jane Adventures (2007, 2008, 2009) and in the 2008 Doctor Who episodes "The Stolen Earth" and "Journey's End".Although she could not save them, she finally knows why they left and is incredibly proud of them.Mysteriously, the camera pans to an old piece of paper reading "Mr Smith, I Need You" on Sarah Jane's desk.Though realising that the time fissure was a trap and initially refusing herself the opportunity to go back in time to find out the reason why her parents abandoned her, that evening she does so, but accompanied by Luke who had anticipated her actions.Rani and Clyde ask Mr Smith where they have gone, and realise that she has gone back to when her parents were alive.
The Trickster then appears before Sarah Jane and mockingly thanks her for all she has done for him.
Then the puzzle box (from the serial Whatever Happened to Sarah Jane? Sarah Jane and Luke spot her mother at the village fete carrying Sarah Jane as a baby.
When they shake hands with Sarah's father, they introduce themselves as David and Victoria Beckham.
Sarah Jane leaves before she is forced to hold herself in baby form, which would have created a paradox.
Upon seeing the date on a newspaper, Sarah Jane realises that 'today' is the day when her parents are about to abandon her.
After telling their daughter how proud they are of her, they both enter the newly repaired car and drive off.