A couple of thousand armed men might easily come through the tunnel in a train at night, avoiding all suspicion by being dressed as ordinary passengers, and the first thing we should know of it would be by finding the fort at our end of the tunnel, together with its telegraph office, and all the electrical arrangements, wires, batteries, etc., intended for the destruction of the tunnel, in the hands of an enemy. We know that ... trains could be safely sent through the tunnel every five minutes, and do the entire distance from the station at Calais to that at Dover in less than half an hour. Twenty thousand infantry could thus be easily despatched in 20 trains and allowing ... 12 minutes interval between each train, that force could be poured into Dover in four hours.... The invasion of England could not be attempted by 5,000 men, but half that number, ably led by a daring, dashing young commander might, I feel, some dark night, easily make themselves masters of the works at our end of the tunnel, and then England would be at the mercy of the invader. General Wolseley conceded that an attack from within the tunnel itself would be difficult if even a hundred riflemen at the English end had previously been alerted to the presence of the attackers, but he doubted that the vigilance of the defenders could always maintain itself at the necessary pitch. And he put it to the committee: "Since the day when David secured an entrance by surprise or treachery into Jerusalem through a tunnel under its walls, how often have places similarly fallen? and, I may add, will again similarly fall?" General Wolseley also found highly questionable the efficacy of the various measures proposed for the protection of the tunnel. He declared that "a hundred accidents" could easily render such measures useless. Thus, for example, he found fault with proposals to lay electrically operated mines inside the tunnel ("A galvanic battery is easily put out of order; something may be wrong with it just when it is required ... the gunpowder may be damp"); proposals to admit the sea into the tunnel by explosion ("an uncertain means of defense"); and proposals to flood it by sluice-gates at the English end ("These water conduits [might] become choked or unserviceable when required" and the "drains rendered useless by treachery"). Then, after pointing out all the frailties of the contemplated defenses, General Wolseley went on to assert that the construction of the tunnel would necessitate, at very least, the conversion of Dover at enormous expense into a first-class fortress and that it could very well make necessary the introduction into England on a permanent basis of compulsory military service to meet the increased threat to Britain's national security.