Susan Campbell nee Foreman (resident of 22nd Century London) says :
You see Grandfather is always doing this sort of thing he's always getting innocent bystanders into trouble and lying through his new teeth.
Half-human, utter nonsense, next he'll be saying he is under 1000 years old.
When we landed on Skaro the Daleks were nothing. Living underground stuck in those flimsy machine bodies, hardly more sophisticated than Dodgem cars.
They didn't even believe in non-Skaroian life let alone time travel, all they were interested in was killing off the Thals.
He had to see the Dalek city for himself didn't he?
He had to put his nose in where it didn't belong.
He nearly got Ian, Barbara and myself killed by wrecking the fluid link to the Tardis and making us wear anti-radiation gloves, one of his silly inventions that never worked.
Before you know it the Daleks know about life on other planets and they know about time machines so it was inevitable that they would invade other worlds and start experimenting with time travel.
Back home this flags up a danger to Gallifrey so they send him back before all this to 'sort out the problem before it get's serious'.
They couldn't have sent someone sensible no they send silly old grandfather and what does he do?
He tells Davros about all the defeats the Daleks would have suffered in their future and Davros programs this into their databanks, what's more they then get the concept of alien worlds and time travel a lot earlier AND have the name of the race that tried to wipe them out before they were born.
It will all end in tears, you mark my words.
I'm just glad to be out of it all, time travel has ruined my ankles.