In the old Dictionary of National Biography, Robert de Vipont shows up with 2 surname spellings: Vieuwpont; Vipont. The pertinent pages are posted in Sources. Robert's bio includes his father, "William de Vieuxpont, who was Lord of Hardingstone, neaat Northampton, in 1999,..."
The online DNB is too expensive -- $29.00 a month or $295 for a year ($24.83/mo.) -- to see if there are updates about the family line.
