In an interview on The Comic Novel

Yes, he’s ‘J.’ isn’t he? The narrator. The story is about three friends taking a weekend trip up the Thames in a rowing boat. But then there’s the dog…

Montmorency…

Montmorency. Who is actually the only entirely fictional character in the boat, but who is absolutely essential to the book, and who emerges, says Jerome, from this part of the inner consciousness which for all Englishman must contain an element of the dog.

Yes it does have that doggy life to it. But they’re also Victorians. Even as they’re going on that vacation, they can’t leave their puritanical selves behind. There’s this weird mixture of making plans, and trying to get up on time, and having this real sense of punctuality and what they want to see and having a schedule and everything, that’s in tension with just how pointless and meandering the whole project is.

Isn’t that a doggy sort of thing?

Perhaps. There’s this moment when the narrator gets up and looks over at George, and George has been talking the whole day before about how he wants to get up and get on with things. And the narrator gets up and Harris gets up and the dog gets up and they look over and George kind of has his knees up in the air and his mouth open and he’s snoring away. And J. gets so angry with him and just says, ‘I always get angry to watch another man sleep, because I think about how he’s wasting his life away.’ I love that part. It’s so funny that he’s looking at this guy and he’s blaming him for wasting his life, and all they’re going to do is sit on a boat and dangle their feet over the edge and eat bacon. You know? The idea that you can separate what’s wasteful and what’s not wasteful when you’re on vacation.