The foundation stone of the new post office was laid by King Edward VII. on the 10th October 1905, and it was opened for public business on the 7th November 1910. The building is constructed of Portland cement concrete, strengthened by bars of steel, on what is known as the Hennibique reinforced concrete system, and it is the largest building that has yet been erected on this plan. It is an all-in-one-piece building, fashioned out of Thames ballast and cement. Not a single steel joist has been used in the centre construction. Barge after barge from Rotherhithe landed at Blackfriars the mud chalk and gravel which dredgers had scooped up in the lower reaches of the Thames. This ballast was carted direct to King Edward Street, passed through a machine which sorts the stones into various sizes, and then turned into liquid concrete by another wonderful machine which mixes sand, cement, and stones together at a rapid rate. The steel rods and bars interlacing one another extend in a network throughout the building like the skeleton of an animal, while the entire system is embedded in a perfectly connected sheath of concrete. The great feature in this system is the immense reduction in wall thickness. The effect is seen in the lightness and airy nature of the building; one's first impression is that it is certainly not built for eternity, as somebody said the granite structures of Aberdeen are. But this is an illusion: the concrete increases in strength as time goes on, and the passing years only make the building stronger and more capable of resisting weather and the strain of the loads which it has daily to carry. Wattles and mud were the building materials of our remote ancestors, and it has been said that we are reverting to the old method, only British mud has given place to British concrete, concrete of Thames ballast and Portland cement. The outer walls are only 7 inches thick, but the frontages to King Edward Street and Newgate Street are faced with Portland stone with granite plinths. To see fully the effect of the reinforced concrete in building one has to examine the back elevations, where there are no stone facings. But even with its false but ornamental front the building has nothing of “the solemn and spacious Greek charm of the delightful old front in St. Martin's le Grand.” The Post Office gains in spaciousness and utility what it loses in architectural beauty. The building consists at present of two parts, a block facing King Edward Street which contains, on the ground floor, the new Public Office, and on the four upper floors the offices of the Controller of the London Postal Service. The other is a much larger block containing the main sorting offices both for foreign and colonial correspondence, and for the E.C. or City district. The actual foundation is only 3 feet in depth, and not one of the floors is more than 3½ inches in thickness.