A relatively late entry to the Lone Pine canon, and quite a bad one to start reading from, if, however you are a confirmed fan, this book is a revelation.
Compared with other young thriller protagonists, e.g, The Famous Five or the Three Investigators, the Lone Piners are unusual in that over time they do actually grow up. It does however take them some time! In their earliest adventures the Mortons are evacuees, in this one their enemy is the son of a German spy, born during the war, yet he and they are the same age.
Rightly ignoring this in a glaring suspension of disbelief, we find the Lone Pine gang growing up fast in this story: passionate kissing, lifelong promises of love, girlfriend-beating (shame on you David!) and leiderhosen all feature, as well as a scene not only outside of Shropshire but out of England!!!Unprecedented!
As usual our heroes triumph by sticking to their 1940s values, whatever their supposed ages, and embarrassing the villains into better behaviour.
I really don't know what today's kids would make of the Lone Piners, even in the '70's when I read these stories they were squarer than double geometry, but Saville's unforced characterisations and love of his chosen setting really shines through.
They don't write 'em like this anymore. Blame the invention of irony circa 1978.