The cast of director Bryan Singer’s fantasy-adventure film Jack the Giant Killer is rounding itself out nicely. Ewan McGregor is in negotiations to join the cast of the fairy-tale update that now includes Stanley Tucci as the villain, Bill Nighy and John Kassir as the two-headed leader of the giants, and Nicholas Hoult (X-Men: First Class) as the titular hero Jack.The story sees Jack on a mission to rescue a princess from the kingdom of the giants. Heat Vision reports that McGregor will play the leader of the king’s elite guard, and fighter of giants of course. The role of the princess for the New Line tentpole has yet to be filled, but the report singles out Adelaide Kane (Power Rangers: RPM) and Eleanor Tomlinson (Alice in Wonderland) as actresses testing for the role, in addition to the previously reported Lily Collins (The Blind Side) and Juno Temple (Greenberg). Filming is set to get underway in late March.