Any basis in fact about Popiel, Piast, Lech, Czech and Rus?

Is there any basis in fact to the tales about Popiel, Piast, Lech, Czech and Rus. Piast was presumably the great-great-grandfather of Mieszko I. BTW anyone know why the first known Polish ruler was referred to as Mieczysław I in Polish schools between the two world wars?

I think there must be some truth here, it happened not that long before writing appeared in Poland...


Here rather not...

I don't know about those guys, but here's not a well known fact.

King Canute was half polish:

"Cnut was of Danish and Slavic descent. His father was Sweyn Forkbeard, King of Denmark (which gave Cnut the patronym Sweynsson, Old Norse Sveinsson). Cnut's mother was the daughter of the first duke of the Polans, Mieszko I;"

Lech, Czech and Rus are 100% legendary. Piast and Popiel - semi-legendary in a Kings of Rome manner.