Ooh him! This is why Catherine married him, according to Dan Jones' The Hollow Crown. There was a law passed in Parliament when Henry VI was still a kid (8 iirc) that she could not marry an Englishman until an adult king gave her permission. The aim of this was to prevent her husband being a potential usurper. However Catherine was still quite young and possibly didn't fancy being a dowager queen for the next ten years, so she married a Welshman. Possibly claiming that being French she didn't know that the Welsh were a despised minority at the time, and so had no idea how far beneath her in birth he was. (Dan Jones implies he thinks she was perfectly aware of this).