Sam Heughan and Caitriona Balfe had insane chemistry in their first Outlander screen test

Outlander's Claire and Jamie Fraser are one of TV's most popular couples, thanks in so small part to the sizzling on-screen spark between actors Sam Heughan and Caitriona Balfe.

And it seems as though the pair don't have to work too hard to keep the fire burning during filming because – as their first ever joint screen test proves – they've always had incredible chemistry.

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ET online released a brand new clip which shows the pair testing out their bond in front of the cameras. Heughan had already been cast as Sam at the time, but Balfe was still auditioning to play Claire and executive producer Ron Moore reveals that this screen chemistry test "was when she literally sealed the deal and got the show".

"They've already got the shorthand of their characters and there is definitely on-camera chemistry between the two. After the scene was over, we just kind of kept the tape running a little bit," Moore continued.

"We just wanted to see them a little bit more relaxed and sort of interacting," he added. "You can see that they're sort of awkwardly aware that the camera is still running, but nonetheless, there is enough spontaneity and genuine affection and good humour between the two of them that it spoke volumes about their potential relationship."

It did, Ron. It really did.

And when Balfe picked up the award for Best Lead Actress at the Irish Film and TV Academy Awards (IFTAs), we could see just how wonderful that relationship turned out to be.