This Is What Happened is the third stand-alone novel by award-winning British author, Mick Herron. Twenty-six-year-old Maggie Barnes hadn't made any friends in the time she'd been in London. She lived in a tiny flat and worked a fairly boring job in the post room down in the basement of the Quilp House. A toxic ex-boyfriend had her avoiding Facebook; she'd dipped a toe into the Twittersphere and had seven followers, several of those probably bots.

When Harvey Wells came along to the café she frequented in the park, Maggie was at first wary. But he knew all about her, and when he explained what he needed her to do, and why, she was both flattered and excited. The idea that she could do something worthwhile for her country was rather thrilling.

Dickon Broom had a not-quite PhD in Philosophy at Cambridge, and worked as a language instructor. He’d had a good position at Marylebone Intensive School of English until a student made trouble for him. That rather queered the pitch at his last interview for a teaching position, and these days he relied on giving private lessons (not ideal) for an income. But now he had another problem to deal with, one that stood in the way of the life he deserved to have

Meredith’s younger sister had apparently been missing for two years. She felt bad about that: they'd lost contact after their parents’ funeral. The police didn't seem interested, treating the whole thing as a case of someone who had decided to disappear, so Meredith was making her own enquiries, and now she had someone in her sights.

Herron’s third stand alone is a little different, but still has many of his trademarks: it has all his careful scene setting; his characters are quite believable; their dialogue natural. While the astute reader will, by the first third of the story, have figured out much of what is going on, there are still a good number of twists, surprises and red herrings to keep it interesting.

The humour is there, but much more subtle than the often laugh-out-loud moments in his Jackson Lamb series, and mostly quite black. Readers hoping for any Slough House character cameos will be disappointed, but fans knowing Herron’s tendency to kill off characters will be racing to the dramatic final pages to discover who survives. Excellent British crime fiction.