The Iron Sheik is a (presumably Arabic) Spark of legendary renown, as well as a good friend and former traveling companion of The Heterodyne Boys and Baron Klaus Wulfenbach (and maybe Trelawney Thorpe). Little is known about him, but he is a popular figure in adventure stories ✣ and with traveling Heterodyne shows ✣ and he really did build that Mechanical Camel ✣ from The Heterodyne Boys and the Race to the West Pole. Oh, and he thought it was a good idea to send his younger son, Z, to live on Castle Wulfenbach for lessons in sparkery, perverting the laws of science, subjugating the pesky peasantry ✣ and possibly recklessness ✣ . Well, that last one seems to be rubbing ✣ off ✣ .
The Iron Sheik as portrayed by a member of Master Payne's Circus of Adventure
While the Heterodyne Boys have disappeared and Klaus has been too busy playing kindergarten teacher tyrant to the sparks and royal houses of Europe to go adventuring ✣ , it is unclear what exactly the Iron Sheik has been up to since The Other War, although there's been mention made of an "Iron Caliphate" ✣ which may have conquered Egypt, so it sounds like he may have done all right for himself. He apparently still trusts Klaus as a good role model for his children, so whatever worried Barry seems not to have fazed him in the least.
Though the Iron Sheik's real name is unknown, based on Arabic naming conventions and Z's full name, Sulimân al-Sinhâjî seem like a safe bet for his given and family names. Whether he too has a couple of other names sandwiched in between is anybody's guess.