The Cooper S has been good news for Birds. It has sold dozens of Hartge engine conversions, plus a goodly number of exhausts, wheels and tyres, and on the evidence of our Fast Fleeter it fully deserves its success, though no doubt the availability of the Works engine conversion - and others - will reduce demand. We've been thoroughly chuffed with our car, particularly the way the power keeps rushing in towards the red line - it's exactly what the Cooper S needs, transforming it from quickish to genuinely rapid. The other thing that's transformed it has been the fitment of the Pirellis in place of the standard run-flat Dunlops, livening up the slightly 'dead' chassis feel, so I was intrigued to see what effect even more extreme rubber would have.

Just as the Asimmetricos sharpen up the handling, the Neros take it one step further. The nose of the Cooper S now feels positively on edge, the steering lighter, the standard car's rather stodgy responses a distant memory. The flipside is a slightly stiffer, knobblier ride, but it's a reasonable trade-off.

It's a similar story with the 'M3-style' four-exit exhaust. At idle and under acceleration from low speed it provides a welcome burbling counterpoint to the supercharger whine, though on a steady or trailing throttle there's a slight boominess that could just become wearing if you weren't in the mood. The cost of all this? ΂£1750 for the engine work (not bad for almost 50 extra bhp), ΂£927 for the Spirit four-exit exhaust (there's also a good-looking Hartge twin-piper for similar money) and ΂£2430 for the wheels and tyres, which are more of an aesthetic choice.

The Tarox brake conversion costs ΂£1800. The beefy callipers and grooved and cross-drilled discs look the business, and there's no denying that they bring considerably more bite to the braking performance - and no doubt eliminate the fade that can blight the standard set-up after a handful of spirited trackday laps - but they may be a bit extreme for anyone but the hard-bitten trackday goer. Upgrading the pads is probably the best option for most Cooper S pilots.

We remain big fans of the engine conversion, and we'd be tempted by the exhaust if we planned to hang on to RX52 for longer, but the winds of change are blowing through the Fast Fleet (beg pardon) and the Coop will only be here for another month or two. We'll miss it.