The Quene's Head/Duke's Head
This is a pub en route to Sto Lat, where Mort realises he has a temporal problem that won't go away even after determined application of scumble: If the landlord's shirt is yellow, it's the Quene's Head and has a crudely executed but recognizable picture of Queen Keli hanging outside the door. If the landlord's shirt is green, it is called the Duke's Head, and has a crudely executed but easily recognizable and in fact politically advisable portrait of the Duke hanging outside the door.
Mort gets to see both. Hence his recourse to Scumble and the lack of surprise shown by the patrons when he screams that "it's coming through the wall!" "It" being the interface between two realities, the shrinking one inhabited by Keli, and the larger one where the Duke rules, remorselessly wiping it out as reality re-asserts itself.