THIS ugly duckling has turned into a swan.

Aston Martin has built a hot hatch worthy of James Bond by shoehorning an enormous V8 under the bonnet of its smallest model, the Cygnet - the micro car that the British sports car maker added to its fleet solely to comply with Europe's harsh emissions laws.

The introduction of the pint-sized fuel sipper - which is a rebadged Toyota IQ - reduced the group's overall footprint allowing it to keep sending out big thirsty V12-powered machines.

However, now the company has done a complete U-turn for a bespoke customer, adding a fuel guzzling V8 in place of the standard tiny four-cylinder and creating a bonkers hot hatch that is anything but environmentally friendly.

The naturally aspirated 4.7-litre V8 (320kW/490Nm) - borrowed from the previous generation Vantage S - provides an intense power boost compared to the 1.3-litre (72kW/123Nm). Aston Martin has not revealed fuel use figures but the V8 claims 12.9L/100km in the Vantage S.

Numerous upgrades (no surprise) were need to accommodate the engine and its brutal outputs.

Aston Martin's custom arm - Q by Aston Martin - fulfilled the customer's request, bracing the car's chassis and body to prevent warping, adding a seven-speed transmission capable of harnessing the V8's urge and fitting a limited-slip differential to get the power down.

Upgraded electricals, exhaust, cooling and brakes also keep the mini-monster in check.

At 1375kg - almost 50 per cent more than the donor car - the Cygnet just had to have beefier suspension and dampers.

The Cygnet can sprint from 0-100km/h in just 4.2 seconds (down from 11.8 seconds in four-cylinder form). The donor car's top speed, a claimed 170km/h, gets blown into the weeds by the hot-hatch version's 273km/h.

The Cygnet's racing credentials have been pumped up with the addition of Recaro racing seats with four-point harnesses, removable steering wheel and a motorsport fire extinguisher.

Sporting Aston Martin's classic green and yellow livery, the custom Cygnet is on show at the 2018 Goodwood Festival of Speed this weekend.

A similar Frankenstein vehicle was built by an American company that fitted a Toyota 86 with a V8 from a Ferrari 458.