We only did it, really, so as to get into conversation with B.
Munn, grocer, and extract information without rousing suspicion.

You cannot be too careful.

However, when we had said it was first-class ginger-beer, and paid for it, we found it not so easy to extract anything more from B.Munn, grocer; and there was an anxious silence while he fiddled about behind the counter among the tinned meats and sauce bottles, with a fringe of hobnailed boots hanging over his head.
H.O.spoke suddenly.

He is like the sort of person who rushes in where angels fear to tread, as Denny says (say what sort of person that is).
He said-- 'I say, you remember driving us home that day.

Who paid for the cart ?' Of course B.Munn, grocer, was not such a nincompoop (I like that word, it means so many people I know) as to say right off.