As I heard the story from Alex - albeit many years later - he married her because he loved her, whether pregnant or not, and was upset when she left him for Ewan. I clearly recall him making a rather bitter joke backstage at a gig, talking about himself being down a mine "hewin' ma coal! hewin' ma coal!" Who will ever know now, except Peggy...

But - if she needed to marry an English person to return to Britain, why not Ewan himself? Could he not travel to Paris for some reason?