Alas, HM the Queen didn't actually sit on the Iron Throne, this occurred during a visit to Belfast and the set of HBO's Game of Thrones. She has much more comfortable places to sit and a vast myriad of cars.
Her relatively new state Bentley is quite a large car and it is one of a kind. The Queen's affectations for Land Rovers are well known. In fact, she was a mechanic in World War II and knows her way around a car, though I imagine her knowledge of ECUs is pretty limited. The Queen even has a custom Mercury Zephyr — thought to be the predecessor to the minivan and SUV in many ways.