The pilot of a helicopter that crashed into an inn while trying to land was focused on a bollard when the blades ripped into the building.
And a report into the 2015 incident found that valid permission was not obtained for the helicopter to operate in Ireland.
"Because the helicopter was an ex-military aircraft, permission to operate the helicopter in Ireland was required from the IAA (Irish Aviation Authority).
"The IAA advised the investigation that a request for such permission was not received," a report by the Air Accident Investigation Unit (AAIU), said.
The owner of the helicopter - who was not flying it at the time - was caught on video trying to move tables as it closed in on the "unsuitable" landing space.
It slammed into a timber-clad wall of the Rustic Inn, in Abbeyshrule, Co Longford.
The helicopter was destroyed in a matter of seconds and the building received significant damage.
There were three people in the function room on the other side of the impact.
One received a cut under his eye and another person fell as a group of onlookers ran away from the crash.
Miraculously, neither the pilot, nor his passenger, were harmed in the collision.
They were able to climb out of the broken cockpit canopy.
The report, released yesterday by the AAIU, found the pilot had tried to land in an area "wholly unsuitable for a helicopter landing".
The pilot was attempting to land on a narrow canal bank between the Rustic Inn and the Royal Canal which was said to have "numerous physical obstacles and aerodynamic hazards".
Investigators said that neither Waterways Ireland nor the owner of the Rustic Inn were asked for permission to land.
The owner of the inn was inside the building when the crash happened.
He said he "attempted to go out the exit door down at the far corner (of the function room) and was obviously under a bit of pressure trying to open it because of the force of the helicopter outside blowing the wind".
He said he heard a bang and the three people in the function room ended up on the floor.
A window on the ground floor was broken and glass and debris were strewn across the room.
A radiator in the first floor bedroom was torn from its wall mounts.
The pilot said he was "completely aware" where the helicopter's blades were in relation to the side of the building.
He told the investigation team he was "concentrating on a bollard, which I knew was there for tying down the boats on the side of the canal and I was concentrating where that was to the skid".
He said that he "turned over to look for it and lost concentration".
The aircraft did have permission to fly in the UK.