Not Sandy Mitchell. Seriously compare their photos as it is eerie.
David Annandale is a writer of the Black Library and a really cool guy. You want to find this man if he comes to a convention near you and shake his hand: full respect is earned and deserved.
Why you ask? What is the main work he is known for so far? Chronicling the life and deeds of Commissar Sebastian Fucking Yarrick that's what. Yeah, that's right, he has written about one of mankind's greatest (and oldest) badasses. And let us not ignore that he wrote the great novel about how Castellan Crowe is really awesome and not a Mary Sue hailing from the old archives penned by our Spiritual Liege.
On the side David has also been having some fun telling us all about his favorite baddest psychic motherfucker in the galaxy having a really good time being a total boss RAGING on some Chaos Sorcerers and another tale for the Titan lovers on how they can wreck up a lot of stuff FOR THE EMPEROR while kicking Chaos around. Also gave a bit of love to Lemartes and why he could kick the entire ANGRY MARINES into following his mad hatred of the enemy for a while before having a planet smashing destruction derby event with Commissar John Fuklaw as the judge. The Space Wolves would obviously be providing the ale for that epic competition as their show of love and appreciation for David's work on their happy little WolfyWolfWolf clan.
He has been contributing to the Warhammer: Age of Sigmar and Horus Heresy history too for a change of pace every so often. You can also find some of his writing with The War of The Beast that is sufficiently manly. GW occasionally like to let him off the leash to see how crazy awesome he can get (IT'S A WALKING CITY!), which makes them a hoot to read.
The first novel he wrote was Chains of Golgotha, where he rightfully depicts good ol' Yarrick as an unstoppable man who's only stopped by the greatest threat: Ghazghkull Thraka (he's the one who made Ghazzy's High Gothic quote, by the way). GW seemed to like this depiction and gave him permission to write to more stories about the Commissar, one focused on his young days, and that turned out well.
He's also going to write a novel regarding Neferata in her current status in the age of sigmar.
For a laugh if you ever meet David, ask him about Godzilla as he is a true fan.