We once had a case where a client, knowing that he had a terminal diagnosis, decided to get married to his long term partner thinking that would mean she would inherit his whole estate. He already had a will leaving everything to her. Unfortunately he did not tell us of his plans and he omitted to make a new will with rather unfortunate consequences because the law of intestacy then applied.
The point to remember is that marriage will cancel an existing will unless the will in question has specifically been made in anticipation of the marriage. A key point often overlooked.