The Cleaner, by Mark Dawson

This is the first is Mr. Dawson's series about hero John Milton.   Milton is a British assassin, working for a deniable government agency after a long and successful military career.  His designation is "number one," meaning he's outlasted all of his predecessors which is apparently the seniority system, as new hire assassins start as "number twelve."

It is an interesting story and I'll read the others in the series (if they are discounted on Kindle occasionally).  I read another of Mr. Dawson's books and it was -- just okay.   This one is better.  Except.

Except that at the very beginning of this novel, things went poorly.  On page 24, Milton is on a subway (Underground) platform.  On page 26, he's at a local hospital having accompanied a stranger he encountered on the platform.  On page 27, his care is conveniently parked next to the hospital.   Oh dear.   This sort of continuity error is completely preventable.  

The Cleaner - John Milton #1 (John Milton Series)