A secondary but important character in ROGUE SWORD is Brother Hugh de Tourneville, a knight of the Knights Hospitallers of St. John of Jerusalem/Rhodes/Malta. Brother Hugh's name seemed familiar, and I found his surname in THE HIGH CRUSADE.
A few quotes are indicated. The protagonist is Lucas Greco, who is waiting at the beginning of Chapter I to meet a new friend: "He stood in the Augustaion, waiting for Brother Hugh de Tourneville to meet him as they had agreed." Later in the same chapter I read: "this gentle, drawling second son of a Lincolnshire baron..."
Next I found this in Chapter I of THE HIGH CRUSADE (Brother Parvus narrating): "I was born some forty years before my story begins, a younger son of Wat Brown. He was blacksmith in the little town of Ansby, which lay in northeastern Lincolnshire. The lands were enfeoffed to the Baron de Tourneville..." (Baron Roger).
I was surprised ROGUE SWORD and THE HIGH CRUSADE had a connection of any kind. For one thing, THE HIGH CRUSADE, while a serious book, is often rollicking. ROGUE SWORD, by contrast, is a fierce, grim, and bloody book.
It was the year 1306 when Lucas Greco first met Brother Hugh de Tourneville. THE HIGH CRUSADE begins in 1345. My guess is Brother Hugh was the younger brother of Baron Roger's grandfather Nevil de Tourneville (mentioned in Chapter IX of CRUSADE). The Tourneville family was also said to be descended from a bastard son of William the Conqueror.
THE HIGH CRUSADE was first published as a magazine serialization in 1959 and published as a book in 1960. ROGUE SWORD was published in 1960 and reprinted by Zebra Books in 1980.
I also thought of how, in Chapter XV of ROGUE SWORD (and various other pages) Poul Anderson seem to have accepted the hostile view of the Knights Templar spread by their enemies. However, the last Time Patrol story Anderson wrote: "Death and the Knight," gives a less starkly negative view of the Templars.