Autocar has obtained tantalising details of a secret Bentley off-roader powered by a 450bhp 6.0-litre W12 engine that, if put into production, could radically alter the status quo at the upper end of the four-wheel-drive market. Codenamed BY616, the luxurious offering is among a number of proposals put forward by parent company Volkswagen in recent months as a means of further expanding the Bentley marque against a backdrop of surging sales, renewed brand awareness and an expanding customer base.