Can You Remember The Name Of This Movie? help me remember pwease??

i watched it when i was little in the 80's. it may have been made in the 70's though.

its about a boy who is a prince ..i think. i think in the movie they all have english accents. anyway, its about him trying to "save the day" by killing a guy that lives in a big castle, i remember he walks through the forest with his friend and they wear a cape that makes them invisable, there are like all kinds of knights or whatever trying to capture them the whole time...

he ends up in this cave and a man in the cave makes them a sword. i remember the man in the cave said that he makes them for the bad guy that is in the castle too. but he makes them a special sword that can kill that bad guy...

the lil boy ends up killing the bad guy that lives in the castle,and when he kills him, his heart turns into a rock or concrete? or something like that. and at the end he finally comes home and i remember he is in a rose garden and his dad hugs him.

HEEEEELPPPP? HEHHEHE THANKS YALL