The Doctor and Victoria are taken back to the Goodge Street base by Colonel Lethbridge-Stewart where the Doctor becomes convinced there is a traitor in their midst.
Did You Know?
When Jamie and the driver Evans stop in the tunnel so that Evans can buy from a vending machine, the chocolate bar he picks is "Camfield's", conveniently named after Douglas Camfield, the director of this series and many other Doctor Who series. See more
Referenced in Evolution of the Invasion