The Prime Meridian runs through Greenwich.
This is why London gets to straddle both hemispheres.
About 70% of London is in the Western Hemisphere and 30% in the Eastern Hemisphere.
North Greenwich, Royal Wharf, North Woolwich, Woolwich, Woolwich Arsenal
Pedantry note: The precise dividing line between the Western and Eastern Hemispheres depends on which Greenwich Meridian you choose.
The original 1884 meridian passes through the AiryTransit Circle at the Royal Greenwich Observatory.
The current IERS Reference Meridian, as used by astronomers and GPS, runs slightly further east.
Across the London area this creates a strip 102m wide which is in the Eastern Hemisphere according to the first meridian but in the Western Hemisphere according to the current meridian.
Locations in this ambiguous zone include the Blackheath tea hut, the Cutty Sark pub and the Sainsbury's inside the Stratford Centre.
* Stratford, East India and Wood Street stations lie on the original meridian, so would be in the Western Hemisphere if you choose the current meridian.
† Stratford High Street and Highams Park stations lie on the current meridian, so would be in the Eastern Hemisphere if you choose the original meridian. Hither Green is the only London station to straddle both hemispheres no matter which meridian you choose.
