My mother in law was caught over the weekend with her boyfriend in the family home whilst the grown up children resident in the home were away on holiday and the father in law/husband was looking after his mother at the house one door down. Father in law came back to a locked door and mother in law came down and unlocked it, only for him to discover there was another man in the house. She is known to have previously had numerous affairs. During the time we lived with them I have seen her extremely drunk several times a week, verbally and physically abusive towards husband, her husbands elderly mother and grown-up children and a 4-week stint in prison for drink driving. Father in law runs a very lucrative business (half in his and half in his brother's name) and is concerned if he divorces her she will get a considerable undeserved sum. Can anyone advise if this is the case? How easily can he divorce her if she doesn't agree to the terms i.e. Financial settlement? She has previously deserted the household for an extended period of time (approx. a decade) but has been back in the house for around 5 years. TIA.