"Amazing, yeah," Robert agreed vaguely. "Brilliant."
But all the same... if he was to reveal himself.... No. Let her be happy with the doctor. The Doctor was safe, if rather boring. What was he but an unnecessary irritation to further separate her from her family?
"Well, I think our circle extraordinarily lucky to be so shockingly lively. I have no doubt we'd find Robert as easily as it is to look into a mirror. He's probably alive somewhere." i.e. in the garden.