Our launch report of the C4 made the point that, unthinkable as it may have seemed just a few years ago, the most expensive model in the range is a turbo diesel. And here it is. There are several C4 diesel engine options, two of them being differently powerful examples of the same 1.6-litre unit, but the top dog is the excellent two-litre HDi, with its impressive combination of performance and fuel economy.
The performance is due to the 138bhp maximum power output, which happens to be exactly the same as that produced by the two-litre petrol unit used in the VTR models. In terms of top speed and 0-62mph acceleration the two engines give almost exactly the same results, but when it comes to economy and CO2 levels the HDi leaves the VTR standing.
And since the diesel is at its most powerful when turning over at 4000rpm, as opposed to 6000rpm for the petrol, the former feels much quicker in normal road conditions - quicker, indeed, even than the 180bhp VTS C4, which starts to come on song just as the HDi is waiting for you to change up a gear.
Not for the first time, this is a diesel which makes you wonder why anyone would choose the equivalent petrol model in the same range. And if you imagine that one possible reason might be the increased noise levels of the diesel, I'm here to tell you that that doesn't apply here. The range-topping Exclusive trim level (like the VTS, and optionally on the VTR) includes laminated side glass which does a superb job of keeping decibels out of the passenger compartment.
Cars in Exclusive trim are very well-equipped, but the C4 is already comfortable without the help of any extra toys. The front of the cabin is roomy (and feels even more so thanks to the large windscreen and considerable acreage of nearly flat fascia top), while the rear is spacious enough for the class. Boot volume is 320 litres from the parcel shelf down, before you start folding down back seats.
My favourite bit is the steering wheel, or rather what appears to be the central boss. From the moment you first turn the wheel it becomes apparent that the boss isn't actually part of the wheel at all, but a separate item which stays in the same position regardless of what you are asking the front wheels to do.
By these means Citroen has dealt with all the problems of fitting minor controls to the wheel and having them floating out of reach as soon as the wheel is turned. It's a brilliant solution, quite in keeping with Citroen's reputation as an innovator.
So is my second favourite bit. The C4 uses digital instruments, which rarely fill me with joy, but in this case they are located in a panel in the centre of that large expanse of dash-top. In daylight, it's lit from behind by whatever is coming through the windscreen, so it is more visible in bright weather and more subdued in dull conditions, just the way it should be. In these high-tech days, this is a rare example of a car feature which is more effective precisely through being as simple as possible.
My least favourite bit is the fact that this medium-sized car somehow combines the sharp handling of a small Citroen with the ponderous ride of a large one. Turn-in is crisp, and lateral grip is splendid, but in this form the C4 takes forever to deal with any kind of bump, as if it had decided it wanted to be a bus when it grew up and was practising for the day it achieved its ambition.
I realise that the C4 isn't meant to be a sport car - not in this form, at least - but that doesn't mean it shouldn't be nimble and easy to drive. The heaving and wallowing were a constant annoyance from the day I first drove this car to the day I handed it back, and make up the principal reason why I don't think I would want to buy a C4. It would only be fair to add that the ride would be less of a problem if you spend most of your time driving in town and on motorways, and also that if you like driving medium-to-large Citroens you're going to love this one, since it rides pretty much the way the BX did twenty years ago.
Citroen describes the C4 as "an extremely serious alternative to the current crop of rivals", which it defines as the Ford Focus, Renault Megane, Vauxhall Astra and Volkswagen Golf. In this country it's going to have a hard time coming close to any of them in sales terms, but to individual buyers it perhaps sits alongside the Megane as a quirky choice for those who consider the other cars in the list to be too square and un-hip.
