She is Doctor Who's most famous assistant since its 2005 revival, while he was an unknown actor propelled to fame when chosen to star in the BBC series.
And now it seems Billie Piper and Matt Smith had more in common than their love of the Time Lord - three years before the latter landed the show's eponymous role.
Pictured holding hands at a Surrey fete in 2006, the pair stroll together through the crowd, drinking Pimms and enjoying the sunshine.
At this point, the two actors had just been reunited on the set of ITV2's Piper vehicle, Secret Diary of a Call Girl, in which Smith had a minor role.
They had previously worked together on BBC drama The Ruby in the Smoke.
Although Smith and Piper never announced they were officially a couple, a friend who was with them on the day they visited the fete says their chemistry was unmistakeable.
'They were very touchy-feely and seemed really at ease with each other,' they said. 'Everybody assumed they were a couple by the way they were acting.'