Gradlon the Great (Gradlon Meur) was a semi-legendary 5th century "king" of Cornouaille who became the hero of many Breton folk stories. The most famous of these legends is the story of the sunken city of Ys. He is supposed to have been the son of Conan Meriadoc.
According to some legends, he was in love with a magician called Malgven. Gradlon had many ships he used to wage war against the faraway countries of the North. An outstanding strategist, he won most of the battles and pillaged the vanquished, amassing great wealth.
One day, his sailors tired of fighting and refused to continue to lay siege to a castle. The sailors returned home and he remained alone in the North. When he was alone he saw a red-haired woman: Malgven, Queen of the North, standing in front of him. She told him, "I know you. You are courageous and skillful in fighting. My husband is old; his sword has rusted. You and I are going to kill him, then go to your country of Cornouaille." They killed the king of the North and went on Morvarc'h ("sea horse" in Breton), Malgven's magical horse. It was black, spit fire from its nostrils and was able to gallop on the sea. They caught up with Gradlon's vessels, but the approach of Morvarc'h caused the fleet to flee.
She's like a swallow that flies so high
She's like the river that never runs dry
She's like the sunshine on the lee shore
She loves her love and love is no more
It's out in the meadow this fair maid did go
Picking the lovely primrose
The more she plucked the more she pulled
Until she's got her apron full
She climbed on yonder hill above
To give a rose unto her love
She gave him one, she gave him three
She gave her heart for company
And as they sat on yonder hill
His heart grew hard, so harder still
He has two hearts instead of one
She says, young man what have you done
How foolish, foolish you must be
To think I loved no one but thee
This world's not made for one alone