Las Vegas, NV (LAS) to London-Gatwick, UK (LGW) $483 round-trip, incl. all taxes.
With fares to London still unusually high for this time of year this great fare is a nice relief!
Available through the end of March with a 7 day advance purchase restriction. Flights are also available from Las Vegas to London-Heathrow (LHR) for about $15 dollars more. Use the Orbitz flexible date search to find availability.