Given how rare this car is, and how it stands out amongst all the other dark colored automobiles, this could be a fun reference to James Bond, as besides the spy genre of the Mission: Impossible saga, British Intelligence is also part of the plot in this movie, and active in that very same scene. At the opening of the Ball Scene, in the exterior of Blenheim Palace, Woodstock, Oxfordshire, a silver Aston Martin DB5 is clearly visible parked in the front spots.
It is unknown how much Pearce and Staples had written for the film, or how much of their content made it into the final film, but Pearce was acknowledged for the story, and McQuarrie is credited as the Screenwriter.