Up to 500 people are expected to attend a homecoming party for John Downey in Ireland.
The former Hyde Park bomb suspect is likely to be greeted by friends, family and senior Sinn Fein politicians including Gerry Kelly at a Donegal restaurant on Saturday. He was imprisoned for the last nine months while awaiting trial in England.
Critics branded the event a "ghoulish celebration" but an Irish public representative said he was an "unassuming" man who should never have been arrested.
Kenny Donaldson, who represents 11,000 terrorism victims in Northern Ireland, said: "He will have a degree of folklore no doubt within the republican constituency.
"The victims are going to feel totally and absolutely disgusted."
The social event is being held at the Lagoon restaurant in the village of Termon in Donegal's north east. Previously fund raisers to help pay for his defence were staged there.
It is situated eight miles from Letterkenny, the region's main town, on the edge of a national park and with stunning views of some of the country's most rugged mountains. The population numbers several hundred.
Among those attending will be Pat Doherty, a West Tyrone MP who does not take his seat but who played a key role in Sinn Fein's rejection of legislation which would have given fugitives from justice an effective amnesty almost a decade ago.
Old Bailey bomber turned peacemaker and Stormont government minister Mr Kelly is also likely to take part.
John McCafferty, speaking for the restaurant, confirmed 4-500 people were expected at the venue, which is more normally associated with weddings and birthday parties and known for its tasty sizzling steaks. It also promises buffets of vol-au-vents and chicken wings for less formal gatherings.
"It is good to see a bit of business, we accommodate all types," Mr McCafferty said.
The family-run eatery and guesthouse is well-known locally.
Donegal County independent councillor Michael McBride lives nearby.
"If you are a victim you will always want to see that justice is done but in this case the man has not been prosecuted," he said.
But he added: "Many people have come home for different reasons and no great parties are thrown."
Seamus O'Domhnaill, a Fianna Fail councillor who knows Mr Downey well, said that after he was arrested last May the council unanimously supported a motion seeking his immediate release.
"We would welcome the decision that he be released, given the fact that the proceeding document (judgement) produced ratified that he should never have been arrested."
He said Mr Downey, an oyster farmer, was a very active member of the community.
"He was very unassuming and very involved in everything."
Jim Allister is leader of the hardline Traditional Unionist Voice (TUV) party which has one seat in Northern Ireland's devolved assembly and opposes power-sharing with Sinn Fein.
"This ghoulish celebration will sicken people across Northern Ireland and the rest of the UK," he said.
"It is a telling reminder of the nature of Sinn Fein and their total insensitivity to victims and their unfitness for government."
Pearse Doherty, a member of the Irish parliament who represents part of Donegal for Sinn Fein, said it was a free entry event being held to thank hundreds of people from across the county and further afield who helped raise funds for Mr Downey's defence.
Danny Kinahan was a serving member of the Royal Household Cavalry when he was best man at Lt. Anthony Daly's wedding in 1982.
Four weeks later, Lt Daly was one of four soldiers on ceremonial duty on horseback in Hyde Park on their way to Buckingham Palace when they were murdered by the IRA nail bomb.
Mr Kinahan commanded his burial party and has become an Ulster Unionist member of the Stormont assembly.
"I am appalled," he said.
"My reaction to these reports of a homecoming party is one of utter disgust.
"Sinn Fein really is rubbing salt into the emotional wounds of the family and friends of those who died on that terrible day in 1982.
"This man should be on trial in a court of law, not living it up in a pub in Donegal.
"This is almost literally dancing on the graves of those who were blown apart, whilst on ceremonial duties.
"It is in incredibly bad taste and brings shame on those who are organising the event.
"I really feel these people are demonstrating the worst kind of 'who cares and so what?' attitude, so often typical of Sinn Fein."