LONDON (AP) — Like a spy in the night, writer Mick Herron’s success has been stealthy. It took a while for the world to catch up with him. A decade after he introduced a crew of flawed secret agents caught between sinister plotters and cynical spymasters in the novel “Slow Horses,” Herron is a best-selling thriller writer who has been likened to John le Carré and won a coveted Golden Dagger award from the Crime Writers’ Association. The seventh novel in the series, “Slough House,” is out this week, and a TV series is in production with an A-list cast led by Gary Oldman. But initially, few took notice.