The first time had been an accident; the Doctor hadn’t wanted another travelling companion, not after Rose, and Donna had been annoyed about getting abducted from her wedding. It hadn’t exactly been an auspicious start, and the events that followed… Well, it was understandable that Donna hadn’t been willing to uproot herself from her familiar life and take off into the unknown. It was too soon.
Now though, Donna was all set, in fact she was amazingly organised. The Doctor found that a bit disconcerting, but…
“Here it is then, the TARDIS. Welcome aboard.”
This was going to be amazing.