The previous paragraph established that the Australian-made car (the Holden) was considered of inferior quality. In the second paragraph, it is then pointed out that the Vanguard, like some of the cars in the family of cars named the Royal*, was made in Britain. Therefore, by the very fact that the Vanguard (and some of the Royals*) were British-made, they were automatically better than the Holden, which was Australian-made.
*NOTE: "Royal" is probably the name of a series of car. I am assuming that you were confused by "the Royal family," thinking that this means the British monarchy. Instead, you should read this expression as "the series of cars named Royal."