The Westside to London overnight
Los Angeles to London is 5,440 miles. The Gulfstream G650, Global 6000 and Falcon 8X fly it non-stop in about ten hours with the jet stream behind them. A heavy jet such as the Legacy 650 stops on the East Coast or in Canada and lands about two hours later.
The eight-hour time difference favours an overnight flight. Leave Van Nuys at 7 pm, sleep, and land at Farnborough at 1 pm the next day. Van Nuys restricts the loudest aircraft after 10 pm, so a very late departure may mean Burbank or LAX. VIP airliners depart from LAX.
London hosts many large-cabin aircraft, so a round trip with the aircraft waiting in England usually costs less than two one-way flights.