Originally Posted by AndyPatterson

This is why the Washington Post travel section reporters, during the weekly chat, ALWAYS recommend arriving in the port city the day before the ship is to sail! This is true even for afternoon sailings. Judging from your itinerary, you were originally to arrive in LHR in the morning of the same day as the departure from Southampton. Was there any reason why you could not fly to LHR a day earlier, and overnight either near the airport or in Southampton? Sure, it would cost an extra day's hotel stay, but you don't have to worry about missing the boat.