SUBARU'S fastest and most powerful Impreza ever - the WRX STi ‘WR1’ - is about to enter dealer showrooms, with more than half of the 500 limited editions already spoken for.

The special edition Impreza WRX STi costs £29,995 on-the-road and features a host of technical and visual upgrades.

First unveiled in January at the ‘Autosport’ show, the Prodrive-developed WR1 has received official Subaru (UK) engineering approval after recording best performance figures for a road-going UK-spec Impreza.

For example, 60mph is reached in 4.25 seconds with the 0-100mph time at an equally impressive 10.67 seconds. Prodrive technicians also logged a quarter-mile time of 12.8 seconds, while the top speed is limited to 155 mph.

Externally, the new WR1 is instantly recognisable thanks to its ice-blue metallic paint plus driving lamps and a stainless steel mesh grill.

Interior changes include anthracite instead of blue suede-effect seats, a special gear knob and imaged carpet mats. The tax disc holder is engraved with the special edition number.