A slice of sponge cake and a hearty round of "Happy Birthday" to the Rotherhithe Tunnel! Not the nearby Brunel-designed Thames Tunnel, (the world's first underwater tunnel, lest we forget) but its quieter, lesser-celebrated neighbour that ferries road traffic underneath the Thames from Southwark to Tower Hamlets. It turns 100 years old today. Opened in 1908 by the future King George V, Rotherhithe was the first road tunnel linking north London with south, and......