Helmut Panke likes peeling onions. It is the BMW chairman's favoured way of illustrating the core values of one of the world's best-known carmakers.

Strip away the outer layers, he says, and the core is to be found not in the landmark cylindrical towers of BMW's headquarters in Munich, but in a cluster of modest buildings in Garching, a small town on the city's outskirts. Together they make up BMW's "M" division.