When you live in a castle, you can't own any old car. You need a car that is as stylish, graceful, and poised as the crown princess. You can't come ambling up the lane in your 2008 Honda Accord, and for the love of all that is good in this world, leave the Bugattis and Ferraris in the cleverly disguised garage. The one possible exception to the 'no flashy cars at the castle gates' rule is the Porsche 911, which is only acceptable to leave out if it's silver, black, or a nice, deep, elegant blue.
Ideally, though, you're going to want a classic car in front of the castle. Cadillacs from the 1910's and 1920's are excellent choices, as are most cars from the fifties and sixties. It is my unprofessional, untrained opinion that the 20th century simply stopped making good cars after the sixties, so please don't park your 1982 monstrosity in front of my castle.
Of course, there is more to cars than their appearance. Driving in a stately manner is an import aspect to your appearance as a member of the royal court. The general rule is this: the older the car, the more noise it makes, ergo the less time you should spend driving it for the good of everyone in a five kilometer radius.
You might ask, "How, then, am I to get about if I cannot drive as frequently as my heart desires?" The answer is simple. All you have to do is have a sentry escort you to the stable, order the stableboy to saddle up your prettiest horse, and ride off into the sunset alongside your favorite prince(ss).
Disclaimers, notes, and post-scripts: Kaija barely knows carburetors from coolants. She also doesn't mean to offend anyone, least of all the royal families of the world. She's just a lowly servant girl scraping out a pittance of a living in someone else's grand palace. Well, not really, but you get the point. If you have any complaints or cries of outrage, please direct them towards the BBC because Top Gear is literally the only way I have learnt of cars past the day I was three and pointed at a lorry and said 'ca.' My mum said "close enough" and ever since I've been terribly, terribly confused. That never really happened; love you mum!