London (UK) and Upper Darby, Pennsylvania (USA) are separated by the Atlantic Ocean. There is no land route; distance cannot be measured as a single "drive" or "direct" path.
Travel requires a transatlantic flight (approx. 7–8 hours to Philadelphia/Philadelphia International Airport) plus ground transport to Upper Darby (~20 min). Total door-to-door: ~10–12 hours.
Great-circle (air) distance: ~3,550 miles (5,700 km).