Roots: The style of the script is somewhat typical of public display skits. Sarah mentions Stirling Moss and British Leyland. Cowboy movies (the arrival of the US cavalry)
Goofs: The Daleks describe two "humans" in the Whomobile, but the second is never identified.
The US cavalry? Perhaps the on-track display might have explained that one...
Dialogue Triumphs: "Hey, crikey - the Daleks and... and Aggedor!"
Dialogue Disasters: "Yeah, give it to them - smash them!"
"Oh, come on, the US cavalry, wherever you are"
"Put that in your Dalek pipe and smoke it!"
Double Entendres: "Here, I hope your metabolism can withstand Matron's bed bath"
Continuity: The Dalek patrol is aware of the Whomobile and its connection to the Doctor. Tracking the vehicle through space and time, they report to the Dalek Supreme and have with them [an?] Aggedor. Their retreat in the face of the US cavalry and their intention to take Sarah back to the Dalek Supreme for interrogation suggests that their mission was intended to be clandestine rather than an all-out attack.
Sarah Jane is taking the Whomobile for a test run around Goodwood Racecourse. The Whomobile has an Emergency Rescue call button which allows Sarah to talk to the Doctor at UNIT HQ (presumably it contacts the Doctor, rather than HQ.)
The Doctor is at UNIT Headquarters having his metabolism checked over on the Brigadier's orders, the Brigadier thinking he is not safe in Bessie, let alone the Whomobile.
Links: The Doctor mentions Bessie. Sarah recalls meeting the Daleks (Death to the Daleks) and Peladon.
Location: Goodwood Racecourse, Sussex (1974?)
The Bottom Line: "I think the Doctor will be well-pleased with the way I handled things."
Rather ridiculous, but good-natured and clearly intended for a broad audience. The ten minute episode is almost a one-hander for Elisabeth Sladen (Jon Pertwee is heard only briefly), and is significant for being the only recorded story where the Whomobile is referred to by that name, but otherwise it's not surprising that the recording languished in BBC Archives for over thirty years.