Once upon a time (1883, and until 1977!) an incredible pipe network existed below London streets: the London Hydraulic Power Company. It powered incredible things, pushing compressed water from the Thames, into workshops, hotel & flat lifts, cranes & various mechanical things... 
The London Hydraulic Company's water pressure lifted the curtains @TheatreRoyalDL, rotated stages at @PalladiumLondon, lifted Leicester Square Theatre's organ, the Palm Court orchestra platform and provided @TowerBridge's backup power. An incredible power.
Elsewhere, the Manchester Hydraulic Power Company's water pressure not only powered warehouse cranes - but re-wound Manchester Town Hall's clock and pumped air thru @ManCathedral's organ. There's equipment preserved at @msimanchester too. en.wikipedia.org/wiki/Mancheste… (ht @EddyRhead)
Once London's 150+ mile hydraulic power network finally closed in 1977, it was bought up by Mercury Telecommunications. They used the pipe routes for cables -inc the old Thames Tower Subway rail/foot tunnel - & are still used today. Images from @subbrit: subbrit.org.uk/sb-sites/sites…
There’s a higher res version of that first map - and Liverpool’s Hydraulic Power network - here, but the original source of the print isn’t noted flic.kr/p/ac7KDH
