Matthew Farrer
One of the writers for Black Library, did the Shira Calpurnia novels making it one of the only novels with the Adeptus Arbites as the main characters, and are pretty good reads at that; the first, Crossfire, probably being the best of the bunch, a detective procedural/thriller against the backdrop of the grim darkness of the 41st millenium. The last of the trilogy, Blind also provides a rare glimpse into the details of the lives of Imperial astropaths. Writes a bunch of short stories that wind up in anthologies. Happens to be one of the few authors for Black Library who does not live in the UK. In this case he is from the land down under. Contributed greatly to our perception of Angron through the story "After De'shea".
Is not Steve Lyons.