SINN Fein’s largest-ever donor, who died in Pembrokeshire last year, has been called a “rebel with a cause”, however questions have been raised about the man’s mental health.

William E Hampton, who died last year aged 82, donated £1.5million in his will to the Irish republican political party.

Since Mr Hampton’s death, questions have arisen surrounding his mental health, with reports that he mutilated himself “some 40 years ago”.

Irish media have quoted a report by The Times that said Mr Hampton cut off his penis after being accused of having an affair with a neighbour’s wife.

Before the incident, he is reported to have walked into the road in Rainham, Kent, and said: “I’ve never touched any woman and I never will”.

Rosalind Murton, a friend of Mr Hampton who he met in a mental health ward, told the Belfast Telegraph: “He was a lovely man but he has some issues.”

Sinn Fein’s (SF) president Mary Lou McDonald called Mr Hampton a rebel with a cause.

She said: “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.

“I can only say Billy was a rebel, a rebel with a cause. He clearly shared our goals.”

Mr Hampton had also been suffering from a mental disorder at the time of his death, which may have caused delusions, hallucinations and depression.

The Belfast Telegraph reported his death certification said he was frail and had schizoaffective disorder and died of respiratory failure and end-stage chronic pulmonary disease.

Ms McDonald from SF said it would be “inappropriate to comment” on Mr Hampton’s mental health issues.

The Electoral Commission (EC) said they have “no plans” to investigate the record donation, saying it was permissible.

An Electoral Commission spokesperson said: “We are not investigating the donation received by Sinn Fein from Mr Hampton. The donation reported by the party was permissible as the donor was on a UK electoral roll within the five-year period prior to his death.

"Political parties must report all donations and loans over £7,500 if accepted by the central party and over £1,500 if accepted by an accounting unit.

"Political parties must only accept donations from permissible donors. It is the responsibility of political parties to check the permissibility of the donations they receive and to ensure they have systems in place to maintain their compliance with the law."

Belfast-based O Muirigh Solicitors, which oversaw legal proceedings for the will told RTE that Mr Hampton's will was made in June 1997.

Senior SF members are reported to have attended Mr Hampton’s interment in Hannahstown Cemetery, Belfast.

An FOI request revealed a SF representative travelled to Pembrokeshire in February this year to ensure the donation was permitted under electoral law.