Battle weary: enjoyable if very messy romp involving crowned heads of Europe, a secret society and international master criminals. By contrast, her Poirot books are as disciplined as a police report. The main enjoyment here is as a period piece, a vanished England which still had an empire and foreigners are a source of amusement or irritation (though she pulls a neat sleight of hand on this), but you’ll go for it if you like your entertainment laced with xenophobia and mildly anti-Semitic tropes that were de rigeur back then - though at least on the latter she seems to have partly relented in later life. “By far the least awful of the early romps,” says Robert Barnard. The bright young things depicted here may not be amusing to everyone but they’re nicely drawn and up for fun, although this can’t ameliorate her snobbery and prejudice.