The supermini is a compact car designed to sip fuel around town and make commuting and parking easy. Equipped with minuscule engines, they wouldn’t be winning any performance awards. However, the Skoda Citigo built by Darkside Developments turns the definition of the supermini on its head.

The biggest change made to the Citigo is replacing its 1.0-litre naturally aspirated three-cylinder petrol engine with a 2.0-litre turbodiesel. Darkside Developments are specialists in tuning diesel engines, so the TDI engine was a natural choice for this project.

The engine develops 263bhp and over 360lb-ft (488Nm) of torque - an extra 189bhp and 290lb-ft (418Nm) more than the most powerful Citigo available. Extra performance can be called upon thanks to a WON Revo 250 nitrous kit, which ups the output further. Power is transferred through a six-speed manual transmission to the tarmac via a Volkswagen 4MOTION all-wheel-drive system, with a Quaife limited-slip differential on each axle.

You might think this would be the perfect car to take on one of our RUSH driving routes, however, this particular Citigo isn’t road-legal. It’s made for track use only, which is evident in the stripped-out interior featuring an FIA-spec roll cage and OMP steering wheel. One of my favourite motorsport modifications is the letterbox-style polycarbonate windows, which add to the race-prepared feel of the car.

This Citigo borrows parts from across the Volkswagen Group portfolio to transform it into a true track weapon. Darkside Developments even added Porsche four-piston callipers for the two braking systems. One is designed for circuits, with 312mm Brembo front discs, while the other is built for drag strips and features smaller 288mm Brembo discs.

The car has been comprehensively re-engineered, but the styling remains close to standard. Using stock body panels, the only major exterior modifications are a set of 17” Skoda Octavia wheels, polycarbonate windows, a vinyl sun strip, projector headlights and a ducktail rear spoiler. A closer look reveals a Darkside intercooler and a side-exit exhaust pipe ahead of the rear wheel arch.

To the untrained eye - or even the trained eye glancing in their mirror on a circuit - there is little to distinguish it from a regular road-going variant. Undoubtedly, it will cause quite a stir on track days as it humbles more exotic machinery.

The impressive and extensive engineering is reminiscent of the V8-powered Aston Martin Cygnet, which similarly started as an unremarkable city car before being comprehensively modified to accommodate the 4.7-litre engine from the V8 Vantage, at a customer’s request. While the V8 Cygnet is unlikely to come up for sale anytime soon, this Citigo has just found its next owner. The car has been auctioned via Collecting Cars, selling for £8,970 - a bargain for a car that has undergone such a major overhaul to become the ultimate supermini.