b997eee8_CCG___What_s_That_Inside_Joke___In_joke
[Card] What's Under Heathrow? [Exp.] Inv [Type] Ref [In-joke] 
The title is a joke about the amount of advanced technology left in the past for Heathrow airport to be built over (in The Visitation and Time-Flight).
Unauthorized Dr. Who CCG - What's That Inside Joke?
In-joke