The crew of a ship that went down with eight men aboard in "extraordinarily violent seas" believed they were under pressure to complete the voyage, investigators say.

The Cemfjord was sailing between Denmark and England when it capsized in the Pentland Firth on January 2, 2015.

The cargo ship overturned so quickly its crew were unable to issue a distress signal and the incident only came to light a day later when a passing ferry spotted the Cemfjord's upturned hull near Stroma.

A search launched in the wake of the sinking was called off when no trace was found of the Cypriot vessel's eight Polish and Filipino crew.

A 15-month long inquiry by the Marine Accident Investigation Branch (MAIB) has now concluded the sinking was avoidable.

Investigators noted there were "significant" safety problems with the Cemfjord's rescue boat launching arrangements and its bilge-pumping system.

They said the crew underestimated the severity of the weather when they sailed into the Pentland Firth and they were not prepared to deal with emergency situations.

MAIB chief inspector Steve Clinch said: "The MAIB investigation found that Cemfjord capsized in extraordinarily violent sea conditions; a fatal hazard that was predictable and could have been avoided.

"The decision to enter the Pentland Firth rather than seek shelter was almost certainly a result of poor passage planning, an underestimation of the severity of the conditions and perceived or actual commercial pressure to press ahead with the voyage.

"Critically, this decision will also have been underpinned by an unwillingness to alter course across the heavy seas after the experience of a cement cargo shift in similar circumstances about three months before the accident.

"The appalling conditions and rapid nature of the capsize denied the crew an opportunity to issue a distress message or to escape from their ship.

"Although not a causal factor of the accident, it was also established that Cemfjord was only at sea because of Flag State approved exemptions from safety regulations.

"This tragic accident is a stark reminder of the hazards faced by mariners at sea and the factors that can influence decision making in such treacherous circumstances."