Direct flights: Non-stop flights from RDU to LHR typically take around 7 hours and 30 minutes to 8 hours and 30 minutes.
Connecting flights: If there are no direct flights available or if you choose a connecting flight for cost or convenience, the total flight time can vary significantly depending on the layovers and the airlines involved. Connecting flights can take anywhere from 10 to 15 hours or longer, with stops at intermediate airports such as New York (JFK), Atlanta (ATL), or Philadelphia (PHL).
It's always best to check with your preferred airline or travel website to get the most up-to-date flight schedules and durations, as they can vary based on factors like weather, air traffic, and airline operational changes.