One of the actual guards on gallifrey took Douglas into a transport ship back to his home planet for questioning.
Courtney is spending time with Sebastian, she thinks that she sees leela talking with one of the actual guards until she see her them walking over them, she stands up keeping an eye on Sebastian, the doctor is walking past everyone and towards the tardis not realising that he has walked pasted everyone Courtney coughs trying to get his attention away from entering the TARDIS he realising that he is going to make some form of mistake by leaving his family whom he loves so much.
She slowly walks over to her dad, waits for him to explain why he was about to leave the planet without herself, Leela,k9 and Sebastian she looks at her dad and shakes her head and says "you were going to leave us here like you left Sarah Jane not close to where she used to lived, I know this i used to live on Bannerman Road in Ealing before I moved to North london"
The doctor just stands there thinking about his former friend and companion who he had to leave on earth before the perfectly timed conception in no fault of courtney's but these things happen, he turns around just admiring how strong headed his daughter is , he hopes that Sebastian doesn't gets his mum's stubbornness when he grows up.
Courtney walks over back to the stairs to go to one of the offices to put sebastian for his nap, leela walks over to the doctor so she asks " doctor, who is this Sarah jane person, is she a friend of yours once" he replies "ooh yes, she was a dear friend who I had to leave on earth before coming back and prior having Courtney entered my life then to give up my only child to a human woman who looked after Courtney for the last 27 years'".
cardinal borusa overheard the conversation between Leela and the doctor, he made a bit of a mistake of forcing the doctor to give up Courtney all those years ago, he walked over to the doctor and says to him "I do apologise to you doctor I didn't realise that you sacrificed not having Courtney by your side for the last 27 years would you like to have those years back again by having Courtney's memories erased and things could go back when Courtney was only baby so you could look after her properly this time round"
YOU ARE READING
The Doctors Daughter
Science FictionThis is how the doctor realised that he's got a daughter (4th specially) This is not canon to the doctor who Franchise