As far as Hyacinth is concerned, the ultimate luxury car is a Rolls Royce and she feels the need to test drive one. Understandably, Richard is more than a little nervous about this due to Hyacinth's habit of wanting to buy things that they can't afford.
When they reach the car dealership, Hyacinth purposefully gives the salesman the idea that she and Richard are interested in purchasing one of the vehicles and a test drive is immediately arranged, but first, the salesman has to take a phone call.
Sick of waiting for him, Hyacinth instructs Richard to drive just a 'short' distance so that she can experience the car properly. When they get stuck in a one-way area, Richard has no choice but to proceed further. Out on the open road, Hyacinth directs Richard to take her to a luxury hotel so that she can show off the car. It's unfortunate that Daisy, Rose and Onslow all happen to be present enjoying afternoon tea, and even more unfortunate when Hyacinth and Richard are arrested for car theft!