A woman who lived with her partner for nearly two decades has launched a court battle after his share of their home passed to his estranged wife after his death.
Lawyers for 69-year-old grandmother Joy Williams say the case highlights the need for the law relating to co-habitation to be reformed.
Ms Williams lived with dentist Norman Martin for 18 years, but he remained married to wife Maureen Martin.
Law firm Irwin Mitchell say their client Ms Williams "now risks losing her home" after Mr Martin died of a heart attack in 2012 and "his share of the house and assets passed to his wife".
Mr Martin did not divorce or update his will to "reflect his relationship with Ms Williams".
They owned their three-bedroom home in Dorset as tenants in common, which meant the house did not automatically pass to Ms Williams after her partner's death.
A judge at the Central London County Court is being asked to rule on the dispute.
Both Ms Williams and Mrs Martin were present in court on Monday for the proceedings, which are expected to last until Thursday.
The judge is being urged to award Mr Martin's share in the home to Ms Williams "so that she has some security for the future".
Paula Myers, national head of contentious trusts and probate department at Irwin Mitchell, said: "This case highlights the needs for co-habitation laws to be brought into the 21st century.
"Too many people do not realise the risks of co-habiting without putting their legal and financial affairs in order.
"Couples who co-habit do not have the same rights as married couples or those in a civil partnership. The idea of a common-law husband or wife is an urban myth.
"Couples considering moving in together without getting married should set up a cohabitation agreement. This is a legally binding document that outlines who owns property, how household bills are divided and maintenance payments for children.
"Couples should also ensure their wills are up to date. If the wills in this case had been updated, the case would not have needed to come to court."