Without hesitation, Arden waved his stick at the leading driver, and the taxi swung into a stop with commendable promptness. As Storm opened the door his keen eye detected the automatic lock which nine hundred and ninety-nine ordinary passengers out of a thousand wouldn't have noticed; he marked also the steel netting between the double panes of the window, and observed how neatly the sash had been screwed up so that nothing less than a jemmy would open it. Leaning over to give his instructions to the driver, he saw that steel shutters had been fitted inside the cab against the glass partition between the driver and passenger, so that the chauffeur would be in no danger of being stuck up with a gun smashed through the glass by a refractory prisoner. "Number Ten, Downing Street," said Storm solemnly, and climbed in. The driver himself, with a courtesy unwonted in taxi-drivers, got down to make sure that the door was properly shut, and Storm guessed that when the driver returned to his perch the automatic lock would also be efficiently latched. They moved off towards Piccadilly Circus, where perspiring constables were struggling to man[oe]uvre a dense millipede of cursing traffic round the narrow gallery which was all the route that was navigable until the hordes of navvies who were even then at work had repaired some of the damage done by the last night's explosion. Kit sat back comfortably, crushed out the butt of his cigarette beneath his heel, and lighted a second. Looking through the wire-netted window at the back, he saw that another taxi, empty but with its flag down, tailed along in the rear. He could identify the chauffeur--an unsavoury-looking thug whose license had been suspended indefinitely some months ago after a curious accident which had attracted the fruitless attention of the Public Prosecutor.