Fire Below

Fire Below is a 1930 adventure novel by the English author Dornford Yates (Cecil William Mercer), the fourth in his "Chandos" thriller series and a sequel to "Blood Royal". The book was published in the US under the title "By Royal Command".
Plot.
Chandos and Hanbury are lured back to the fictional Principality of Riechtenburg by a forged telegram.
Background.
In this novel, the author continued to mine ideas from Anthony Hope, specifically "Rupert of Hentzau". Commenting in 1958 through his character Boy Pleydell, Mercer acknowledged resemblances between his work and that of Hope, particularly mentioning "Fire Below" and "Blood Royal".
Critical reception.
The "Chandos" series had made the name of Dornford Yates widely known, and "Fire Below" was as received as eagerly when it appeared in June 1930 as his earlier "Chandos" books had been.
The original dustjacket included the following quotes -