In reply to needvert:
It is important to take the Wikipedia instruction's "2.Tighten the overhand portion of the knot around the standing part" seriously --*seriously* tighten it in tying, for loading will NOT : the risk is that the noose will fold and pull the tail through (and, yes, that will take much force).
If you tie the overhand in mirror image (i.e., reverse every crossing's over/under of the >>overhand<< itself (but not of the main line it's tied around), you will have a similarly bulked-into-trefoil stopper that cannot pull the tail through (as the part pulling pulls upon not only the tail but around the rim of the trefoil). This knot is less quickly formed than forming the overhand noose (backwards "slip knot", if you will), but hardly difficult.
*kN*