The Verdict: Jaguar XJ

Price: £43,995
Engine: 2.7-litre diesel
Performance: 0-60mph in 7.8 seconds, 35mpg
CO2: 214g/km
Worth considering: Mercedes S-Class, BMW 7-Series, Audi A8

An XJ with a diesel engine is long overdue and essential if Jaguar is to keep up with Mercedes, BMW and Audi, who introduced their own diesel saloons with aplomb sometime ago. Luckily for Jaguar, whose sales need all the help they can get, the XJ is a welcome addition to the party.

There are bigger and more powerful petrol XJ engines available, but none come as cheap or with the same fuel economy as the diesel. You may think that Jaguar drivers aren't going to quibble about how much it costs to fill the tank, but with fuel the extortionate price it is, the engine choice will have a serious impact on wallets. For example, the diesel does 35mpg compared with the V8 Supercharged's 23mpg.

The diesel engine doesn't disappoint. Although diesel brings to mind dirty, smelly and noisy vans, the XJ is refined and extremely quiet, although admittedly not as silent as the equivalent petrol engine. But the real problem is not so much the sound of the engine, as the performance. Whether it has something to do with the diesel engine, or the automatic gearbox, or simply that the 2.7 litre engine isn't big enough for a car as big as this, the reaction when you press your foot on the accelerator is disappointing. There is a delay before it kicks in and pulls away effortlessly and gracefully. But I, for one, expected more of an instantaneous reaction.

Taking nearly eight seconds to climb from 0-60mph is disappointing for a Jaguar, particularly as the V8 Supercharged version knocks three seconds off this speed. This aside, the XJ is a fine motor. It's big, wide and long, with plenty of room for five adults. Those sitting in the back may be in for an extra treat, depending on the spec you opt for, as televisions in the front-seat headrests are available. The standard interior feels more budget than the traditional Jaguar, with no polished wood in evidence. The steering wheel is leather, or burr walnut, and you can opt for the walnut on the dashboard or go for the sophisticated aluminium veneer.

The seats may be leather, but one of our reader panel was convinced that they weren't, because "they looked cheap". Again, this isn't what you'd expect from a car at this price, although the 16-way electrically adjustable driver's seat righted that impression a little. What's more, it slides back when you remove the keys from the ignition to enable you to climb in and out without too much effort.

Apart from overly sensitive "intrusion sensors", the XJ diesel handles like a dream, is a pleasure to drive and is beautifully styled, with excellent build quality. Once again, Jaguar is gaining ground on its rivals.

Kim Morgan, 29, radio producer from south London
USUAL CAR: MGF

"It's true what they say: speed bumps really are for the proles - you can't feel them at all as the XJ really soaks them up. But you can tell that it's a diesel - the sound is very distinctive when you start up the engine. As soon as you are moving, though, you can't hear it. The steering is good and I like the feel of the interior styling: it's not overly plush and old-fashioned like the old-style Jaguar but feels modern and well-kitted out. It is effortless in the way it pulls away and overtakes, and glides gracefully. I am really surprised that the seats are plastic, though; for a car this price, you'd expect to get leather. They are leather? Really? They certainly don't feel like it."

John Roberts, 58, landscape gardener from Guildford, Surrey
USUAL CAR: JAGUAR XJS

"I can't get over how sensitive the brakes are: I drive an XJS and they are nothing like as sharp as these. I was surprised at how smooth and quiet the engine is for a diesel; there is more noise from the road than the engine, and quite a lot of the former. The interior is beautiful and I like the outer styling, although it looks like the Mercedes S-Class, which isn't necessarily a good thing. One of Jaguar's strengths has been its classic, distinctive look. I don't think I will be trading in my XJS for one of these, even if there is a surprising amount of space. Ultimately, I prefer more speed and power than you are going to get from a diesel with automatic transmission."

Matthew King, 54, university administrator from Barnet
USUAL CAR: MERCEDES SLK

"It's very opulent, but I would never buy a car this big, although it handles well for its size and the engine is very responsive. The windscreen is heated, but I don't see the point of this and don't like the lines accommodating this function. The electronic parking brake is easy to use, but when the engine is ticking over it's very noisy. For a car this price and quality, I would expect the engine to be much quieter. It could be faster at picking up speed, but I imagine that having an automatic with a diesel engine explains that. The boot is quite big, although not as spacious as I'd have imagined for a car this size. The leather seats are cheapish looking and the clock is tiny."

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