Dan Trent: There's no replacement for displacement

These days we're used to our hot hatches delivering 300bhp or more from turbocharged four-cylinder engines. And that's all very impressive. But the moment you hit the starter button on a BMW M135i that old thing about no replacement for displacement – or cylinders – makes complete sense. And in the modern context, the idea of a turbocharged 316bhp 3.0-litre six in a classic longitudinal configuration and driving the rear wheels of a Golf-sized hatchback still sounds extraordinarily naughty. Ever the masters of working the emissions game to their advantage BMW's engineers somehow managed to make the official numbers look good too – 175g/km and 37.7mpg are enough to look acceptable in 'real world' running cost calculations.

And it's this sense of rebelliousness, and the fact it's wrapped in such understated bodywork, that makes this car such an appealing proposition. Well, that and the way it goes. I ran an M135i  as a long-termer and the cold start bark was so amusing I'd always fire it up with the driver's door open just to savour it. Indeed, the car it reminded me of was the R34 Nissan Skyline GT-R – another icon defined by its turbocharged in-line six-cylinder engine.  

Unlike a Skyline, though, you can go about your business in an M135i and nobody need be any the wiser. Especially one like the example I've chosen from the many available in the PistonHeads classifieds. The eight-speed automatic many were sold with (and my old long-termer had) is a superb transmission but I think I'd have to have a manual, even if it's typically rubbery and long of throw like many BMW gearboxes. You can work around that. A car like this needs to be a manual. 

This £18K example combines understated black paintwork with – joy! – the de-badge option. Apart from the dual exhausts and bigger brakes, nobody would pick it out from a 116d. Brilliant! As far as I can tell it also has the passive dampers, which are preferable to the underwhelming adaptive ones. On the inside, however, it's got some really rather lairy red leather seats to compensate for the understated external looks. I should probably look at a five-door really, being a family man. But the three-door is, to my eyes, a handsome car in a quirky sort of way. There's a hint of Z3 M Coupe 'breadvan' in its proportions, though it remains a Marmite car styling wise. I happen to like Marmite, for what it's worth.

True enough, this is a car all about the engine. And the stock dampers, steering and brakes are nothing special. The fundamentals are there though and experienced tuners like Birds offer sensibly priced upgrades based around Bilstein damper sets and Quaife limited-slip differentials that really realise the potential. While keeping the stealth looks. Sure, a Golf R would probably be faster. But what's rebellious about a fast Golf? BMW's ugly duckling, rear-driven and with an absolute gem of an engine, is a true sleeper and the kind of car that saves its best for the driver. As a sensible daily with a sting in the tail, it's got a definite place on my fantasy fleet. Debadged in sober paint is just the icing on an already tasty cake.