Time was when secret prototypes were wrapped in disguise so you couldn\'t tell what they were. Here\'s one that wears a manufacturer\'s badge and has its own Twitter hashtag on the side.It\'s the Jaguar XF Sportbrake, due in autumn 2012. Get your tweet on.Cars are usually disguised because the manufacturers don\'t want sales of the current machine to take a plunge in the face of news of a new one. But there is no existing Jag estate.So they might as well tease the Sportbrake, on the off-chance some people might say, ‘Wooooah, hold on a minute Mr BMW dealer, I\'ll just cancel my order for a 5-series Touring until I\'ve had a proper look at this Jag.\'An XF estate then. About time too. Jag didn\'t actually plan this car when it originally designed the XF, because Jaguar is a company that has historically played to the UK and US. No-one buys estates in the US, it\'s all SUVs over there (not that Jag has one of those either, at least until 2015).But once Jag had the Tata money and backing, it could start to invest for expansion. It developed a four-cylinder diesel. And it was good. But if you look at sales of the BMW 520d and Audi A6 2.0, what do you see? They\'re mostly estates. So Jag needed a wagon too.Ian Callum\'s people have designed something suitably sleek. It\'s the same length as the saloon. As you can see from the front-three-quarter shot, the rear side glass tapers downwards, so it avoids looking like a National Express. In fact it might remind you of an XJ saloon, because under that disguise, the rear pillars are covered in glossy-black trim that wraps between the tailgate glass and the side windows. You can see from the rear shot the big round tray of a roof spoiler too. Those are temporary rear lights - the real ones will be different from the saloon\'s because the tailgate is wider than the saloon\'s boot lid.Cargo space, I\'m told, matches a 5-series Touring\'s. The rear seats fold properly flat, and there\'s space under the boot floor. There\'s more rear headroom than in the saloon. So it\'ll be a proper contender.But it so nearly didn\'t make it. Jag bosses have told me they realised that unless they rushed the launch, the Sportbrake would have only a couple of years\' life before the next XF came along and rendered it obsolete. So the production people have had to crank it out super-quick in order to satisfy the accountants it\'ll actually turn a quid before it dies.