Nothing is impossible: I just love this bit because River doesn’t even hesitate for a second with her response. Nothing’s impossible - just a little unlikely. And she displays absolute faith and trust here. He says it’s impossible and she doesn’t even for a second consider it might be actually impossible. She knows better. She’s learned differently. And of course she just asks and he answers, despite having just declared it not possible. She knows he can do it - so he knows he can do it. River always knows. And I’m sure it was totally necessary to hold her hand to sonic that bit of cable Doctor. Yup. Absolutely needed.