DID you know that diesel accounts for around a quarter of BMW’s global sales, and for about half of all BMWs sold in Europe? Combining six-cylinder power and refinement with four-cylinder economy, a burn in the X5 or X3 3.0d or 530d instantly reveals why. Now the 1 Series has gone down the diesel route. But to some eyes, with its boldness of design and engineering, the smallest BMW-badged passenger car is arguably the company’s purist, as well as one of its bravest. So does the four-cylinder diesel 120d deliver?