Sir Joseph William Bazalgette (28 March 1819 – 15 March 1891) was one of the great English civil engineers of the Victorian era. As the chief engineer of London's Metropolitan Board of Works, his major achievement was the creation of a sewer network for central London, which helped relieve the city from cholera epidemics, while beginning the clean-up of the River Thames, which had reached a nadir with "The Great Stink" of 1858.
Bazalgette's foresight may be seen in the diameter of the sewers. When planning the network he took the most dense population, gave every person the most generous allowance of sewage production and came up with a diameter of pipe needed. He then said 'Well, we're only going to do this once and there's always the unforeseen.' and doubled the diameter to be used. Every Londoner should be grateful for this foresight as the unforeseen was the tower block. If he had used his original, smaller pipe diameter the sewer would have overflowed in the 1960s. As it is they are still in use to this day.

From Wikipedia.