Friends of a man who left £1.5m to Sinn Féin have said the party could get even more money from his will.
Englishman Billy Hampton, 82, left the money to hit back at the British establishment, according to his friends.
It is understood to be the largest ever known donation to a Northern Ireland political party.
The money was bequeathed by the former market trader, who died in Pembrokeshire, Wales.
“He got it into his head that the establishment was out to get him,” said Dave Morton, 71, a friend of Mr Hampton’s, from Suffolk.
“It probably was all in his head, but he left the money to Sinn Féin to basically say ‘up you’ to the British establishment.”
Sinn Féin vice president Michelle O’Neill has said there is “nothing to see here” after the party was given the donation.
The party said it has complied with all Electoral Commission rules and regulations.
Billy Hampton’s late father, Ted, had extensive business interests in the village of Fenstanton in Cambridgeshire that included property, a transport company and industrial estates, according to Mr Morton.
After his father’s death in the mid-1980s, Billy inherited some of the money.
But according to his friends, Mr Hampton blamed the establishment for his inability to access the full inheritance to which he believed he was entitled.
“He was having problems getting his inheritance, possibly because he had been in a mental hospital, or it could have been for legal reasons we don’t know about,” Mr Morton added.
“In his mind he had been let down by everyone in this country, apart from one or two people who tried to help him.”
Friends of Mr Hampton believe Sinn Féin could end up inheriting more than the £1.5m they have already received from his will.
“From what we could make out in his letters we received, Billy seemed to have the impression that he should have got £7m,” said Mr Morton.
“He [Billy] was not stupid. He was well-educated and if he thought that, I would not be surprised if he was not close.”
Mr Morton said Mr Hampton opted to leave the money to Sinn Féin “to get the last laugh at the establishment”.
“He is probably laughing in his grave right now. He’ll think this is hilarious.”
In a letter written from France in 2000, Mr Hampton said: “Having had mental problems, everyone thinks I am barking mad, a silly Billy goat, and don’t believe a word I say or write. Sorry, it was England that kicked me into the hands of Sinn Féin.”
In his early life Mr Hampton worked as a market trader in Rainham, Kent, fixing second hand drills at his stall called “Bill the Drill”. Years ago he developed psychiatric problems.
After a time in hospital, he adopted a nomadic life, and spent some time in west Cork. He passed way in Wales in 2018, having written his will in 1997.
As well as the Sinn Féin donation, Mr Hampton left £8,000 to be divided among four other people, including £1,000 to the veteran Labour MP Dennis Skinner.
Mr Skinner said he does not recognise Mr Hampton’s name, and unlike Sinn Féin, he has said he will not be accepting the money.
According the Probate Registry of Wales, the will was worth £2.5m, suggesting another £1m worth of assets still have to be dispersed.
The balance could end up going to Sinn Féin because it remains the executors and the trustees of Mr Hampton’s will.
In one letter written in France in 2000, Billy Hampton wrote: “I am much less paranoid than normal, and do not suffer from a persecution complex at all here in France.”
And in the same letter, written three years after he wrote his will, he said: “Sinn Fein will not speak to me now for security reasons.”
So far, Sinn Féin has declined to comment on this or say what it thinks it may have meant.