 Former General Motors boss Fritz Henderson described making petrol hybrid cars as "expensive squared. But making diesel hybrids," he added, "now that's expensive cubed."  So welcome to the world's first diesel/electric hybrid car, an expensively cubist creation from Peugeot-Citro?n. First shown in Paris last year, this new driveline goes on sale in the 3008 SUV in November and in the following five months will appear in the 508 range and the RXH, an upmarket all-road estate. Yet even as it was being launched, rivals were muttering darkly that the Peugeot would be noisy and smelly.  Early drives of the prototype 3008 Hybrid4 were certainly the former, with graunches from the driveline and little evidence that it would be any more economical than a half-decent petrol/electric hybrid. Diesel hybrids haven't been used outside of the locomotive and heavy-plant industries because the fuel economy advantages over a petrol hybrid have been tiny. There's also the fact hybrid cars are principally designed for urban driving in countries that don't like diesels; think Japan and the United States.  So this is the first European hybrid, if you like. Under the bonnet is a standard 161bhp, 2.0-litre turbodiesel attached to a robotised manual six-speed transmission driving the front wheels. a hefty 8kW generator recharges the nickel-metal hydride battery, which lives in the back along with a 36bhp aC electric motor driving the rear wheels.  This provides four-wheel drive without the heavy transfer boxes, propeller shafts and differentials of a mechanical system. Not that a 3008 will do much mountain climbing, but it's difficult to see many drivers not being attracted to the idea of 200bhp and fleet managers spurning the fiscal advantages of 99g/km emissions of CO2 with the all-weather capability of four-wheel drive.  There are some drawbacks, however, not least the ?26,995 price. The cheapest petrol 3008 is almost ?10,000 less and even the cheapest 1.6 diesel costs just ?18,895, delivers 54mpg in the Combined cycle and emits a highly respectable 135g/km. and while the Hybrid4 sports more power and performance, it's also carrying an additional 441lb, which is a rear seat's worth of passengers.  Provided the battery has sufficient charge, the 3008 will proceed in electric mode for a maximum of 2.5 miles at no more than 31mph, although it will maintain a cruise using the battery alone at up to 40mph.  There are four operating modes: auto, which optimises diesel and electric power for efficiency; Sport, which combines engine and motor for maximum performance, but the engine stop/start system remains on; 4x4, where the engine and motor act similarly to Sport but stop/start is disabled and torque build-up is limited at the rear to prevent the wheels spinning; and ZEV, where the car will run as an electric vehicle for as long as possible, whereupon it will automatically change to auto mode. You can shift between modes on the move, but the systems will take a second or two to set up the car as directed.  First impressions are of great refinement, especially compared to early prototypes. The restarting of the diesel engine is particularly smooth, as is the transition between electric and internal combustion drive. The gearbox is smoother than most robotised rivals, too. This has been an extraordinary feat of calibration - Peugeot's engineers have done well.  Sport mode proves that this is a serious performance machine, with a lovely addition to the torque curve in the midrange for ease of overtaking. You can feel the additional weight in the back, especially if you lift off in a corner, bu 