Stop what you're doing. David Tennant has dyed his hair red.

David Tennant's Tenth Doctor may have been seriously disappointed when he didn't have flaming-red hair after his regeneration, complaining bitterly: "Aw, I wanted to be ginger. I've never been ginger."

But now the actor himself has got his hands on some red hair dye and gone to town.

The Doctor Who star surprised his fans when he was pictured at the Good Omens read-through with a brand new hair colour.

It definitely freaked people out, though the reaction was delightful.

So next question: why IS he ginger?

Tennant is set to play demon Crowley in Good Omens, a TV adaptation of Terry Pratchett and Neil Gaiman's classic 1990 fantasy novel. He'll star alongside Michael Sheen, who will play Aziraphale – and who is currently going with a spiky blonde hairdo.

But in the novel Crowley is actually described as having "dark hair". Is the TV show mixing it up?

It could also be the case that he's gone ginger for another role. Tennant is playing the part of Anthony Babington in Mary Queen of Scots alongside Margot Robbie and Saoirse Ronan at the moment.

Or we could be barking up the wrong tree. It's also entirely possible that he just got excited in the hair dye aisle of Boots, grabbed a box of their reddest hair dye and went for it.

Perhaps, like the Doctor, he HAS always wanted to be ginger.