It is expected that north of $6 million will be paid for what is regarded as one of the rarest Bentleys on the planet. When the car goes up for sale at Bonham\'s in June, it is expected to fetch as much as $6.3 million and instantly become the most expensive Bentley ever to be sold at auction. According to various media reports that mantel is currently held by the 1930 Bentley Speed Six Tourer sold for $5.1 million in 2004.The 1929-1932 Bentley 4.5-liter will be the highlight of a seven-car and two-motorcycle collection that belonged to British watchmaker George Daniels, who died last year Bonhams say the entire collection is expected to fetch $12.6 million, and also released in a statement that Daniels once said: \"for all its inconvenience (the Bentley) is a most exhilarating car to drive both on the road and track.\"The red, supercharged single-seater Bentley was once the property of British racing legend Sir Henry \'Tiger Tim\' Birkkin, who, in 1931, set the Brooklands Outer Circuit Lap record at over 137mph.The auction for one of the rarest Bentleys of all time will take place on 29 June as part of the Goodwood Festival of Speed.