Armoured limousines are something most car makers would rather not talk about.The customer profiles involved are notorious and the technology top secret. It is big business though. Mercedes-Benz and BMW have been providing the exceptionally wealthy (or thoroughly despised) with nearly indestructible limousines for years now.With its fourth-generation XJ taking the market by storm, Jaguar realises the value (and potential profit) of marketing an armoured model.The aptly-named Sentinel fulfils this role.Pretty car. Deadly serious business.Riding atop the long-wheel base XJ platform this armoured Jaguar is virtually indistinguishable from its sibling. The armoured inner cell is constructed from high-strength steels reinforced with Kevlar, produced for Jaguar on commission from Centigon - a leading global specialist in vehicle armouring.Thanks to its armour the Sentinel’s kerb weight nearly doubles from standard XJ's 1 755- to 3 300kg. Powered by the 283kW naturally aspirated XJ 5l V8, performance (predictably) suffers. The 0-100km acceleration time (barely) dips under the 10-second benchmark at 9.7 sec, whilst top speed is a rather pedestrian 195km/h. Logic dictates the 375kW supercharged V8 would make a better car to speed away from assailants. Gaining momentum swiftly is one thing though, trying to slow down 3.3t of supercharged XJ is quite another altogether. To shore up the Sentinel’s agility (considering its mass burden) the car's continuously variable dampers have been recalibrated whilst suspension and steering are beefed-up too. The Sentinel rolls along on 19-inch strengthened alloy wheels, shod with special Dunlop 245/45 run flat tyres. Brakes are the high-performance units from the supercharged XJs.BulletproofHow safe is it when under attack from assailants though? Technically the Sentinel is ballistics-rated to the B7 level and offers blast protection against 15kg of TNT. Effectively it renders 9mm fire ineffective; so insurgents with their Makarov pistols will only scratch up the paint. You won't make Dirty Harry's day either as 44 Magnum rounds don’t penetrate the armour. Impressive? Certainly.In the real world, unfortunately, 'sensitive' business deals are done in the Middle-East and Africa, where the weapon of choice is the venerable AK-47. Fortunately Centigon’s armoured reinforcement of the XJ has made even the Kalashnikov’s impact redundant. The Sentinel appears to be the first proper alternative to BMW and Mercedes-Benz's armoured 7 Series and S-Class offerings. Pricing? Well, that is a case for discussion between customers and Jaguar.