It's the car Land Rover can't replace, and this year the all-conquering Defender will get yet another refresh. The hardest working 4x4 in the world gets a new 2.4-litre four-cylinder diesel engine and an updated cabin - the first refreshed 2007 model rolled off the line yesterday. Next year, Solihull will celebrate its 60th year in production.This update is the most significant refresh the Defender has had since 1990, when the car's wheelbases were altered, and its name changed to 'Defender'. It's recognisable by the additional bulge in the bonnet. Under that bulge there's a new 2.4-litre engine with more torque than the outgoing five-pot. It's adapted from the one found under the bonnet of the Ford Transit, so you can bet that it's robust and willing to take plenty of abuse. Out too goes the old car's five-speed gearbox in favour of a new six-speed manual with wider-spread ratios for better motorway cruising and enhanced off-road ability.Inside the new Defender there are also big changes. In an attempt to add a bit of much-needed civility, the car's heating and ventilation systems have been overhauled, and air conditioning becomes an option. The sideways-facing rearmost seats have also been binned for new forward-facing replacements, making it safer for occupants. The Defender's long-lived ladder-frame chassis and aluminium bodywork have been retained, though, and Solihull will continue to offer it in 90-, 110- and 130-inch wheelbases, and with a wide-range of station wagon, flatbed, double-cab and other body derivatives.Sales of the Defender have remained consistent at around 25,000 units per year of late, says Land Rover, with much of the demand coming from large contract orders from various military, public utility and emergency service bodies. Since 1948, Solihull has knocked out 1.8 million Defenders. The car currently supports more than 750 jobs at Solihull, where it’s built alongside the Range Rover, Range Rover Sport and Discovery.