In Murder Must Advertise, Wimsey briefly portrays a charicature of himself as a cold, stiff, conceited, well-educated lord. It's an hilarious episode, since it's a ruse perpetrated by the true Lord Peter (dear Lord Peter!) - quick-witted, playful, noble in the ancient sense.
In Thrones, Dominations, however, not only Wimsey, but also Harriet, Parker, and Bunter are sad, pale imitations of themselves. There's even one scene in which Parker says something abysmal like, "I don't mind if Bunter takes photgraphs. I have seen Bunter's photographs before. They are of a good quality. He knows better than to mess up the evidence, too." Who ARE these people? It's true that Wimsey and Harriet still quote various texts at one another. In the grand style of an ill-begot sequel, however, the majority of the quoting is from Sayer's previous works - half the sentences seem to start with "Remember that time when we...?". There's a very obnoxious mix of constant reference to Sayers' novels, a desire to wrap up all the "loose ends" in them, and complete lack of any resemblence to them.
More upsetting, however, than the problems with style and characterization, is the heavy-handed way in which Walsh handles the moral and ethical dilemmas Sayers carefully developed over the whole of the LPW series. The worst error is perhaps made just in the "wrapping-up" tone that permeates the novel - as if Lord Peter and Harriet had reached their pinnacle, and would not grow any farther. One equally striking, however, is Walsh's incapacity to deal delicately and knowledgeably with the notion of nobility.
Thrones, Dominations may be a decent book. It's not an especially intricate or interesting mystery story - it has none of the technical descriptions and details that characterize Sayers' books. But it's certainly not a Lord Peter Wimsey mystery.