A Qantas spokeswoman said fog was the primary cause of the delay but a mechanical fault was then found when the A380 arrived at Al Ain Airport. Spare parts and an engineer had to be brought in from Dubai.
The spokeswoman said customers were given all of the food on the plane and were given the option to disembark when the delay continued.
Passengers were then offered a room for the night when the plane eventually made it back to Dubai, while others were given the option to fly to London on the next available QF1 flight or partner airline flight.
It's understood the passengers will not be compensated by the airline for their ordeal.
They will have to make any claims through their travel insurance.
Dozens of passengers blasted the airline on Twitter, describing it as "despicable service" and accusing it of "ruining Christmas".
One woman wrote: "Merry Christmas from Qantas, 14hr delay on a plane with no food, 1hr delay at Dubai getting to terminal, cabin crew that don't have any idea and constant lies and to top it off delay to get luggage. Really outdid yourselves this year."
Another man said: "It's sounding like the day was driven more by your errors than just fog."
Other Qantas flights, QF10 bound for Melbourne and QF2 bound for Sydney, also experienced significant delays in London due to the heavy fog in Dubai.
Those passengers were offered the opportunity to cancel or change their flight.
"We know delays can be frustrating especially at this time of year, and we sincerely thank our customers for their understanding as we worked to find the best way to get them on their way as quickly as possible," the Qantas spokeswoman said.
The airline is continuing to monitor the weather conditions in Dubai, which have all airlines flying through the airport, and will contact customers travelling through Dubai if their flight will be impacted by delays caused by the fog.
Customers travelling through Dubai who have not yet begun their journey will be offered the option to change, cancel or delay their flight.
