'X' marks a spot you never thought existed, with speculation that BMW will soon prise open the very skinny space between the X3 and X5 SUVs with its all-new X4.

Mooted for a Detroit motor show global debut in January, the latest BMW crossover will take a leaf out of the X6 in being a sleeker and swoopier version of the second-gen X3 launched here last year.

However, the X4 is expected to go one better (and much harder) than the latter, with high-performance M versions in the pipeline, to give the upcoming Porsche Macan something to lose sleep over.