Abstract: A propeller comprises a hub (1) rotatable about a propeller axis and formed with a hub barrel (1) with a central hub axis that extends radially of the propeller axis, a blade (9) having a support assembly (3) at its inner end received within the hub barrel (1) and including at least one bearing (11,16) that supports the blade (9) for rotation about the hub axis, a locking recess (7,25,33) formed at least in part in the support assembly (3) and at least in part in the hub barrel (1) and a key element (26) located within the locking recess (7,25,33) to restrain radial outwards movement of the blade (9) along the hub axis. The key element (26) is insertable into and retractable from the locking recess (7,25,33) while the inner end of the blade (9) is assembled in the hub barrel (1). The locking recess (7,25,33) extends circumferentially within the hub barrel (1), and the key element (26) is flexible to follow the recess when inserted.