When your boat was brand new Amel typically used a clever knot on all of the halyards and outhaul ropes.
The tail of the rope is whipped with cord back on to the standing part of the halyard which means two things.
1. The knot will never unravel when there is tension on it.
2. You can slacken the knot as much as you like when there is no tension and then the halyard will very easily slide through the gate in the mast. Once you have the halyard back inside the mast them you can tighten up the knot again.
I appreciate this all sounds confusing, but maybe if you have a look at all of the ropes on your boat there might be an original halyard and you will easily identify it as you will see the cord whipping on the standing (longest) part of the rope. The you can see how simple it is.
Years ago I cut off one of these knots from an old halyard and kept in in a drawer so that I could always copy it correctly.
Seafever SM 425