With its long bonnet and rear-wheel drive set-up, the two-seat Z4 is traditional. Over the last 25 years, BMW's two-seat convertible has evolved nicely from the Z1 (1987) into the current Z4.

The latest version has been given a mid-life facelift.

For buyers more concerned with looking the part than enjoying outright serious performance, there is a new 18i badged version (in fact, it is a detuned 2-litre) and we've been testing it.

The 18i's in-line, four-cylinder engine features 'TwinPower' turbo-charging that delivers a peak power output of 156hp and 240nm. Outside, Z4 has evolved at a snail's pace and only car anoraks will spot change, but remember the saying: "If it ain't broke don't break it"!

Z4 remains a muscular sportscar that is shamelessly aggressive. While the exterior styling might not be as disarming as an MX-5's, it has a strong appeal. Let's not forget that performance versions of the Z4 can hold their own against rival Porsches.

Inside Z4 there are some new styling touches and trim variations available. New alloys also feature with a range of new 'V' spoke 17- and 18-inch wheels to choose from. The cabin is spacious and enthusiasts can find a perfect driving position with little effort. BMW's manual seat height adjuster continues to be difficult to use once seated.

As with all two-seat convertible sportscars, the true joy is in topless motoring. The electric folding hardtop's roof may rob the Z4 of a big chunk of usable boot space (unlike the MX-5), but the three-piece mechanism and double-hinged boot is a joy to observe in action.

Z4 is a blast on even the coldest of days: turn the heater on 'full' and the seat heaters to their hottest setting - which feels hot enough to fry an egg - and the Z4 is truly joyous! In fact, driving on a nippy night with the roof down is the best way to clear the mind and put a grin on your face.

Our test car when started defaults to a 'Comfort' drive profile setting but you can toggle a switch to select 'Sport' (that boost power) or 'Sport+' (which, in addition, 'dumbs down' the driving aids). Driving in Comfort mode is a pretty flat experience and your only enjoyment will be from the car's precise steering, good brakes and the wind in the hair. Our advice is to flick it to Sport once you start up and the Z4 will feel adequately powered for daily use.

The Z4 model range starts with the new sDrive (rear-wheel drive) 18i and contains the existing sDrive models, namely the 20i, 28i, 35i and 35is range-topper. The only downside to a two-seater is ease of access for those who can afford it in the first place. Z4 has two long doors and in order to get in and out you need a certain amount of space to swing the door open wide enough. This makes choosing the right parking spot a more demanding exercise as most multi-storey and supermarket car park spaces have shrunk!

The new Z4 is a beautiful piece of design. The 1.8-i may be the smallest, least powerful engine available, but it can deliver driving thrills, when pressed hard. The price tag is high when compared to the excellent Mazda MX-5, but Z4's fit and finish is superior.

Michael Sheridan