The RSPCA has lost a court battle over a legacy worth more than £2m.
Since July 2008, the animal charity has been involved in a legal contest with Christine Gill from Northallerton, North Yorkshire, over her mother's will. The will left her mother's entire 287-acre estate as a charitable bequest – and nothing to her daughter.
The High Court accepted Gill's view that her father had coerced her mother into making the will before his death in 1999, and that she had received repeated assurances that she would inherit her parents' home, Potto Carr Farm in North Yorkshire, when they died.
However, when her mother died in 2006 Christine Gill discovered she would receive nothing.
A spokeswoman for the RSPCA said the court case raised concerns for other charities.
"Throughout this, the RSPCA has been in an extremely difficult position," she said. "The will left by Dr Gill's parents was very clear - in one sentence they left their entire estate to the RSPCA, and in the next they said their daughter should receive nothing.
"In that situation the RSPCA cannot just walk away. In fact we are legally obliged to seek the funds under charity law."
The charity said it had acted in good faith throughout and had offered Christine Gill £650,000 plus her costs.
John Low, chief executive of the Charities Aid Foundation, said the case showed the importance of families discussing a legacy with the next of kin.
"Charities need to be able to focus all their efforts on helping society, rather than spending their time in courtrooms up and down the country," he said. "I would urge anyone who is planning to leave money to charity in their will to explain their plans to their children or other next of kin long before illness and care needs come to dominate relationships."