Two women who say they were misled by their ex-husbands and should get more money in their divorce settlements have won their Supreme Court fight.
Alison Sharland, who accepted £10m in her divorce, and Varsha Gohil, who got £270,000, say the men hid the extent of their wealth when the deals were made.
Solicitors for Ms Sharland's ex-husband Charles said the ruling could "open the floodgates" to thousands of cases.
Ms Gohil said there were "no winners", but both spoke of the pair's relief.
The court indicated that both claims would return to the High Court.
BBC legal correspondent Clive Coleman said it was an "incredibly significant ruling" that meant a division of the parties' financial assets had to be based on a "valid agreement".
"If one of the parties is dishonest, if they are misleading about what their assets are, then this is a very clear signal that the other party can go back to court, can have the agreement set aside and can have the whole thing considered again," he said.
'John' from Kent is divorced and says the ruling is "fundamentally wrong".
"My divorce cost me more than £200,000," he said.
"I am now in my sixties, worked all my life and have lost more than half my earnings, including what my parents were good enough to leave me.
"The system is crazy. Some women set out on a course after marriage to get as much money as possible."
'Joan', who is divorced, said she hoped it would strengthen her appeal case.
"This is welcome news for women - or men - who have fallen foul of the wealthier party in a divorce who have been hiding their assets," she said.
"I had a very comfortable lifestyle until I left my husband. I now have less assets than I did when I went into the marriage."
Ms Sharland, from Wilmslow in Cheshire, believed the £10m settlement she accepted in her 2010 divorce from her husband Charles, a software entrepreneur, represented half of his wealth.
Under the settlement, the 48-year-old would also receive 30% of the proceeds of shares held by her husband in his company when he sold them.
It later transpired he had lied about his company's value - which the financial press estimated to be worth about £600m, when the value used in the divorce case was £47m - as well as plans to float it on the stock market.
Ms Gohil, 50, from north London, accepted a car as well as £270,000 as a settlement when she divorced her husband Bhadresh in 2002.
In 2010, Mr Gohil was convicted of money laundering and jailed for 10 years.
At his criminal trial, evidence revealed he had failed to disclose his true wealth during divorce proceedings.
"I hope that their decision sends out a message to everyone going through a divorce," Ms Sharland said.
"My legal battle has never been about the money, it has always been a matter of principle.
"I entered into an agreement with my estranged husband thinking that it was a fair one."
She said she wanted to move on "safe in the knowledge that my future divorce settlement will be based on the true value of our assets".
Giving the judgement of the court, Lady Hale said Ms Sharland had been "deprived of a full and fair hearing" because of "her husband's fraud".
Ms Gohil said: "There are absolutely no winners in divorce and more than a thought has to be given to the children of families locked in this type of litigation."
James Brown, a partner with JMW Solicitors, which is acting on Mr Sharland's behalf, said his client was "bitterly disappointed that his family will continue to be locked in litigation for the foreseeable future".
"Family law is complicated and entirely discretionary and there could be a danger that this change may open the floodgates to thousands of couples revisiting the agreements they reached," he said.
"Mr Sharland's primary objectives have always remained the same - to arrive at a fair settlement with Mrs Sharland and to make generous provision for his children."