Books like Five Go Off to Camp

This one I remember from my childhood. SPOOK TRAINS! So, once again the two sets of parents jettison their children at the first opportunity, this time sending them to camp on a wild moor in the care of an old school teacher, Mr Luffy. Quite why this man wants to spend his holiday watching over other people's children remains unclear. Anyway, fortunately his interest is in bugs and beetles rather than young boys or girls, and he is largely absent in the story.We soon discover that trains run through tunnels under the moor. This is rather mysterious in itself as tunnels are massively expensive things and usually reserved for going through hills. Anyway, let's buy into the premise that a big network of train tunnels run under the moor, some in active use and some disused. They also find a disused railway yard near a tunnel entrance.The second part of the puzzle is the suspicious affluence of the local farmer whose stepson they befriend.A mad old man with a wooden leg introduces them to the idea of spook trains running on disused lines with no lights. Conflict arises because George, though "only a girl" wants to come with the boys to watch for the alleged spook train. They don't let her.Predictably the spook train is spotted, but when the boys explore the tunnel it went into it seems to have vanished.Separately George and the boys discover the hiding place, get captured, and find that the unreasonably rich farmer is involved. Anne mostly stays at the camp and cooks and tidies. Though she does bring Mr Luffy and the police into play at the end.Oh yes, there are natural caves linked to the tunnel, because EB finds it very hard to write a Famous Five book without a cave in it.The whole train business is rather far fetched. In order to hide their stolen/black market goods the farmer and his allies seem to have renovated an entire train and run it across the moor at night to shuffle the goods into the hidden room they have constructed in the abandoned tunnels. This feels like a ridiculously complicated solution to hiding their goods. There's no indication that the farm is ever raided by police or that the farmer is suspected of any misdoings. Perhaps he could keep them in a barn?In the end the farmer's wife cheerfully sees him carted off to jail ("He's always been so weak.") and the son, Jock, is down with it too. Neither of them seem bothered by the idea that their grand piano, posh car, fleet of lorries, and new tractors may be taken away. The whole thing was "simply smashing" says Jock. Hoorah!Whilst this one does include caves, kidnapping, and the black market, there is no actual treasure this time, no gypsies, and nobody tries to poison Timmy! Join my 3-emails-a-year newsletter #prizes..