The campaign represents the first activity to focus on one specific product and will hope to steal a march on competitors such as Kingsmill, Warburtons and supermarket own-brand products.
The 20-second animated spot, "crust freak", was created by John Webster at BMP DDB as part of the ongoing "Get something good inside" campaign.
It focuses on the established character Hillary and introduces a fresh character in the shape of the family hamster, Percy.
The spot opens on Hillary sitting at a table, with Percy in his cage.
As she starts to eat her Hovis Crusty sandwich it is clear she is enjoying it and as she comes to a point of near ecstasy, the bewildered hamster is forced to hide behind his wheel.
Media planning and buying is by BBJ. Paul Thompson, BBJ's associate director, said: "This is part of an ongoing TV campaign specifically targeting upmarket housewives and tapping into those moments of indulgence."
The ad was written and art directed by Webster, and directed by Grant Orchid through AKA Studios.