Sinn Fein President Mary Lou McDonald says the reclusive English man who left £1.5 million to the party in his will is a "rebel with a cause."
Billy Hampton who died last year in Wales aged 82, was living in a mobile home when he made his last will and testament, in which he left the donation to Sinn Fein.
It is understood to be the largest known donation to a political party in Northern Ireland.
Ms McDonald said the money was bequeathed to Sinn Fein "within all of the rules and regulations and will be spent within the rules and regulations".
"I did not know Billy Hampton but judging from people who did know him he considered this to be a very robust statement against the political establishment.
"He obviously saw in Sinn Fein an organisation that is full square for Irish unity, for progress and for peace and prosperity in Ireland but also a party that stands full square against the political establishment," she said.
"I can only say Billy was a rebel, a rebel with a cause. He clearly shared our goals."
Ms McDonald said it would be "inappropriate to comment" on Mr Hampton's mental health issues.
Ms McDonald was speaking at the party's annual away day in Dundalk Co Louth.
