School-run mums who need space as well as speed will be pleased to hear Audi has launched a family car that can keep pace with a Ferrari.The powerful new R S6 Avant is believed to be the world’s fastest estate. It accelerates from rest to 62 mph in 3.9 seconds and will cost around £77,000 when in showrooms early next year (for delivery in summer).Yet it still has room for five people and plenty of boot space.And given Audi’s popularity among members of the Royal Family, it could be ideal for those preparing for a new arrival.The car’s 560 bhp, four-litre V8 engine, linked to an eight-speed automatic gearbox, gives it a top speed of 189 mph.It uses the same turbo-charged engine found in the Bentley Continental — popular with Premier L eague footballers.The standard model will be limited to 155 mph but this can be removed to give it a top speed of 174 mph, and 189 mph for the topend Dynamic Plus model.A Ferrari C alifornia, meanwhile, will accelerate from rest to 60 mph in 3.8 seconds with a top speed of 194 mph, while a Porsche 911 GT3 R S takes four seconds with a top speed of 193 mph. It can even outsprint Audi’s own flagship R 8 V8 supercar, which accelerates from rest to 60 mph in 4.3 seconds and has a top speed of 184 mph.Audi’s team of engineers performed 5,000 test miles at the Nurburgring race track in Germany.And despite its performance, Audi says the R S6 Avant is still capable of a relatively frugal 28 mpg, which makes it 40 per cent more efficient than its predecessor.But a spokesman from road-safety charity Brake warns:‘There is never a need for a family car to be able to reach speeds of 190 mph, or even 100 mph.’ The taxman is seeking official permission to break Britain’s speed limits. HM Revenue & Customs (HMRC) wants to join the police, fire, ambulance and other life-saving’ emergency services in being exempt from obeying speed limits.No doubt some canny accountant is already drawing up a dodgy ‘speed avoidance scheme’ to help the super-rich avoid penalty points and fines if caught on camera.