After their macarbe mission was complete, the repair drones realised that they still needed a central computer to govern navigation of the ship, in order to get it moving again. They theorised that, since the ship was 35 years old and its name was the SS Madame de Pompadour, that the brain of the actual 35 year old Madame de Pompadour was the only brain suitable for the ship's computer.
In order to access Madame de Pompadour the robots opened time windows across the ship which opened at random points in Madame de Pompadour's life. They searched for a window that would lead them to her when she was exactly 35, however, the Doctor stumbled in on their operation at this point and did his best to prevent them from discovering the right window. In a danerous move, he sealed the time windows whilst he was still in ancient France, risking his own life to protect Pompadour's, and it worked. Cut off from their ship, the Robots deactivated, never to function again. The Doctor meanwhile managed to reactivate one final window to get home.