Use AA's multi-city award-booking engine to put each flight on a free hold. The engine will price the award at 25,000 AAdvantage miles in Economy. Note the record locator, call AA, and ask the agent to reprice the itinerary as a single, one-way award for 12,500 AAdvantage miles in Economy, noting that you will be in London for less than twenty-four hours, and that LGW and LHR are considered the same city (London) for connection purposes.