As the cliche of car sales goes, it is already quite the offer: a rare vintage Rolls Royce, one careful owner. Factor in the enormous windows for maximum visibility, a pennant holder and room for coat of arms of the door, then it is a vehicle that could only be fit for a Queen. A 1950 Rolls-Royce Phantom IV State Landaulette, one of only 18 ever made and used by the Royal Household for more than 40 years, is to be sold at auction for up to £2 million.