BMW is working flat-out to prep its new X5 performance flagship – expected to debut at the Geneva motor show early in 2009 – which borrows the X6’s muscular 408bhp twin-turbo V8 for a 155mph punch. It’s a step closer to the full-blown Motorsport X5 that BMW had vowed it would never build.

While there’s nothing exactly sluggish about the current top dog X5 – the 4.8i is powered by a 355bhp 4.8-litre V8 that will rocket the BMW to 60mph in 6.5 seconds and on to 152mph – the addition of the X6’s blown 4.4-litre V8 to the range will make the X5 as quick as a Porsche Cayman S. Expect it to hit 60mph in just 5.5 seconds and be electronically reined in at 155mph. That’s pretty brisk for an thick-ankled off-roader that weighs the wrong side of two tonnes...

Hmm…I'm thinking about the fuel bills in this BMW X5

Well, with an estimated price tag nudging £60,000 it seems unlikely that most buyers will be concerned with a car that barely manages 23mpg on the combined cycle and has a CO2 posting of around 300g/km.

You’ll be able to spot it when it looms in your mirrors though – like the X6, the hottest X5 will have a revised nose housing much larger air intakes to feed the blown engine, as well as a more profiled bonnet. It will, in short, look like a right beast. Expect the suspension and brakes to undergo the necessary upgrades, too.