For some years now, I have had in my head the idea that when Dunsany was approached in 1946 by August Derleth about Arkham House publishing an omnibus of some of Dunsany's earlier books* (published in the United State by John W. Luce & Company), Dunsany wrote back to Derleth, saying that he hadn't heard anything from Luce in over a quarter of a century, and he directed Derleth to "rob Luce without mercy."
Except that's not correct. What Dunsany actually wrote to Derleth, on the 11th of September 1946, is less tart: "Luce has sent me no payment, or even a letter, for over a quarter of a century, and I do not imagine that any rights he may have had can survive that. So you may ignore Luce."
Why did that more deserving phrase carve its way into my memory so strongly? The answer is that I have read it in a slightly different form elsewhere, and my memory had intermingled the details.
Here is Arthur Machen, writing to Vincent Starrett on August 23rd, 1921, about some of his books not then published in the United States, including The House of Souls, published in London by Grant Richards: "If you have the chance, rob Grant Richards without mercy. He has robbed me, so slay and spare not."
The sentiments are pretty much the same in the letters of both writers, but Machen's phrasing is clearly more memorable.
I'm glad now to get the wordings and attributions corrected.
*Nothing came of this.