Rogue's Yarn

Vernon must have been a fan of Freeman Wills Crofts. The detective here could easily have been Inspector French - a portly pipe-smoker determinedly dismantling an alibi involving a devilish bit of engineering on a means of transport. He gets stuck but finally makes the breakthrough. He needs to travel to France, three times I think. He responds with stoicism to the doubts of his superior. A little more affability would have made the match perfect. There is surely a debt here to Crofts.