James Bond screeches around hairpin bends in them with a beautiful woman at his side, while they are the car of choice for European royalty in which to parade themselves around the Continent’s more opulent capitals. Now, at last, the opportunity to pop out to the supermarket behind the wheel of an Aston Martin will be opened to the more conventional motorist. The Aston Martin Cygnet — a new “luxury commuter concept” car, according to its marketeers — is to be built on the base of Toyota’s existing iQ city car and is likely to be available for less than...