10 Dec, 12:23
Ireland's John Lacey will referee his first ever RBS 6 Nations match in February, while Alain Rolland is also included in the Elite Panel in what is his last season.
Tykes director of rugby Phil Davies confirmed from the club's Headingley base: "Derek is an exciting player who will challenge Scott Benton for the starting scrum-half position. He is looking forward to the challenge of coming over to England and furthering his career."
Prior to moving to Munster, he played for Leinster and also featured in the Heineken Cup for them.