The city that has one of the world’s oldest and greatest bridges spanning the Thames river also created the world’s first tunnel that went under it. Where horses, and later cars, could pass over the bridge, the pedestrian foot tunnels allowed people to cross the river without running the risk of being trampled or run over. The noted Scottish civil engineer Alexander Binnie, who once worked at the London docks and knew the difficulties dockworkers sometimes faced in getting across convinced the city council to commission a tunnel to help ease the strain.

On this day, August 4, in 1902, the 1,200-foot long Greenwich foot tunnel opened to allow Greenwich to the Isle of Dogs, where most of the docks were located at the time.

Although the first underwater tunnels were built in Britain, they were invented across the Channel, in France. In 1818, Marc Brunel, a French engineer, invented a “tunnel shield”, essentially a rectangular cast iron wall with numerous small windows that could be inserted in the ground beneath the river floor. Workers could open each window, dig out a little dirt, and then close it back up. The wall itself could move horizontally via screw jacks, and where it moved from workers would reinforce with bricks and mortar.