The 1961 Jaguar Mk X (or Mark Ten) is certainly the Jaguar that most non-enthusiasts have never heard of. Everyone knows the E-Type, and the XJ6 was around for so long that its impossible not to know it, but the Mk X? Anyways, it was introduced in 1961, and was the widest car, at 6 feet 4 inches, that you could buy in the UK at the time. It was a smooth, stylish luxury sedan, as well appointed and refined as cars costing twice as much. It also could handle quite well, considering its size, and was extremely comfortable. It did not receive universal approval, for the usual reasons: it was too big, the steering was too vague, and the seats, too mushy.
The Mk X was powered by the triple-carburattor 3.8-liter straight-six from the E-Type, which was eventually upgraded to 4.2-liters, and a total output of 265 horsepower. The big car could reach a top speed of 122 miles per hour and accelerate to 60 in just under 10 seconds, which is an acceptable level of performance for a large luxury sedan in the early 60s.
Over the years, various improvements were made to the 1961 Jaguar Mk X, not only to the engine, but to the power steering and seats in order to address customer concerns. While it was retired in 1970, the Mk X shell remained, in the form of the Daimler DS420 limousines, which stayed in production until the 1990s.