As your other thread in going from a 4x4 to a saloon car. When we decided to buy the caravan, a large heavy single axle Weight (MTPLM): 1711kg the only 2 saloon cars matching were the Mercedes W221 S Klasse, and the Audi A8, both in long wheelbase form for the kerb weight. The BMW 7 series and Jag XJ were not recommend for towing, but I can't recall the exact reason. Fortunately we had the S Klasse, that when we bought it we had a motorhome and no requirement to tow a caravan.
A rear wheel drive, diesel with an auto box is not the best to get off a soggy grass pitch with or without caravan, especially with staggered 19" wheels and wide tyres :evil:
The new W222 S Klasse is now too light to tow the caravan, it's nearly 300 Kg lighter than the W221. The only model in the range you can get a towbar factory fitted is the basic model.