Flanders was a very powerful French territory, so the marriage would actually do more for William's status than Matilda's. According to some stories, Matilda saw this and said she would never marry someone of such lower status, whereupon William road to Bruges, and either 1) forced his way into her bedroom and beat her, or 2) met her on the road, dragged her from her horse by her hair, and "courting her" in the mud. Here father was outraged, but was stayed from getting revenge by Matilda saying she would marry William or no one.
What kind of man was he? The only surviving piece of him is a femur, from which the height of 5'10" can be deduced. This would make him tall for his time. He was considered a great fighter and very strong, able to draw bowstrings that others could not. A contemporary, Geoffrey Martel, Count of Anjou, says he was without equal as a fighter and horseman. Although considered greedy and cruel by contemporaries, he was also praised for his piety.
William turned to the abbot of Bec, Lanfranc, for help with the pope. Lanfranc also opposed the marriage, so William exiled him from Normandy, but at the last minute forgive him if Lanfranc would take on the task of convincing the pope to relent. A pope finally approved the marriage some time in the 1050s, but it was probably post-ceremony: William and Matilda had gone ahead and married without papal approval, it is assumed. One of the persuasions that supposedly worked to get the pope on their side was the founding of two monasteries, one by the groom and one by the bride.
The union produced four sons and several daughters. There is no inkling that William had mistresses on the side. As a mother, she made sure all her children were well-educated.
He trusted Matilda to rule when he was absent, and she was involved in many of the affairs of state. The illustration shows both of their signatures on the Accord of Winchester, which established the primacy of the Archbishop of Canterbury over the Archbishop of York. (It did not go over well with everyone.) After he went to England (and she bought a ship with her own money to contribute to the invasion), she stayed in Normandy until 1068, waiting to be crowned Queen of England until it could take place at Pentecost (11 May 1068). Phrases were added to the ceremony elevating queenship to be equal to kingship in terms of divine authority.
In the summer of 1083 she fell ill, and died on 2 November. William swore to give up hunting (his favorite pastime) as an expression of grief. She was buried under the floor at l'Abbaye aux Dames in Caen. When her skeleton was examined in 1959, it was determined that she was 5' in height, a typical stature for the day.
And now we turn to an earlier moment, when a member on England's royalty visited William and, perhaps, made him a promise.