The 29-year-old singer and the 23-year-old actor son of Jude Law and Sadie Frost began seeing each other after meeting on the set of new movie 'Twist', where she plays the Artful Dodger and he is starring as Oliver.
A source told The Sun newspaper's Bizarre column: "It has been simmering for some time after they started working together.
"People made a few comments about the chemistry straight away and the gossip started from there. But it was only after a while that the attraction really grew into something meaningful between them."
Rita and Rafferty have reportedly been keeping their romance a secret until now but decided to go public by holding hands as they left the British Fashion Awards after-party on Monday (02.12.19). The loved up couple were spotted leaving Giorgio Armani's bash at Harry's Bar together.
The insider added: "Now it's a proper relationship so they decided they were ready to go out as a couple for the first time. They couldn't help holding hands as they left. It's still early days but they're pretty loved-up right now."
Rafferty - who recently told the Evening Standard that he and Rita clicked "straight away" - has worked as a model and 'Oliver Twist' is his first major acting role.
After his casting was announced, a source explained: "'Twist' is a modern interpretation of Charles Dickens' Oliver in which the title character has been reinvented as a streetwise artist living on the streets of modern-day London...
"Rafferty impressed with his screen presence and his edginess brings a whole new dimension to the role of Oliver. It's an all-star cast with David in the mix after arriving at today's first rehearsal - not to mention Rita and Sir Michael Caine."