The construction of the London and Birmingham Railway was one of the greatest engineering feats since the erection of the pyramids. Wolverton Viaduct, Primrose Hill Tunnel, Tring and Blisworth cuttings were all major obstacles, but the greatest challenge of all to Robert Stephenson's skill was Kilsby Tunnel - more than a mile through a hill whose centre consisted of quicksands fed by underground springs and a subterranean lake. It took thirteen pumps working night and day for over nineteen months to staunch the quicksand.