If he arranged to meet with a view to stealing the car, you would have thought seeing the child would make him change his mind.
I can only think he jumped straight in and drove off instantly and never saw the child until it was too late.
That then begs the question...how did the car seller let this happen?
Where does it say it is untaxed, I can't see it? And we don't know the owner had been driving around in it.
It looks as if the owner had only just put his child on the front seat when it happened.
//Describing what had happened when the car was stolen, Maria's uncle said his brother had placed the child on the front seat as he demonstrated the engine.\\
On bbc website it says police said the father drove to the street in Newham to meet a prospective buyer, who then stole the car. Also quotes number plate. Not difficult to check car tax.