These strange craft were to be lashed between a couple of monitors, and so pushed across the channel and up the beach at certain selected points, points that exhaustive air reconnaissance and photography at all states of the tide had indicated as most suitable.
Actual trials of the pontoons and their monitor escorts were made in the secret waters of the Thames, and officers of the Tank Corps would suddenly disappear on unknown missions, to reappear as suddenly with no memory as to where they had been or what they had seen in the interval.
The sea wall itself might well have been designed as a special defence against sea-borne hostile Tanks, its smooth concave face and projecting coping making it absolutely unscalable by an honest Tank.
The wall was of recent construction, and by a fortunate chance the Belgian architect who had designed it had escaped to France with all his drawings.
From his plans an exact reproduction of a length of the wall was made.
There in the experimental ground it stood, perfectly smooth, and worst of all, ending at the top in a curl-over coping.
At least, however, the engineers now knew the extent of their problem.
In the first place, the Tanks had to get up somehow, and in the second place, when they were up they had to help haul up guns and transport lorries.
After “trying on” various devices, the Tanks at last adopted what was practically a portable ramp for the occasion.
The Tank, until it reached the sea wall, carried it well in the air on a long spar supported by wire hawsers.