At long last we have a BMW M5 Touring again! Which, if you’re a parent, or a practical person with a ‘lifestyle’, means this could be all the car you’ll ever want. And if you’re not one of those, then the wobblier estate body and lack of a carbon roof might mean you think the Touring is destined to only ever be a worse version of an M5 saloon. Either way, we haven’t had a big-booted BMW M5 since the V10-powered, E60-generation model, and with all the obvious rivals dead or dying out, there’s a rather large gap in the market for this new 717bhp über-estate. So, what chance does the M5 Touring have at greatness? To find out, Top Gear Magazine’s Deputy Editor, Ollie Kew, has been in a studio with one, while Editor-in-Chief, Jack Rix, has been driving a prototype…