The light from Flannan Isle flashed twice every thirty seconds. In good weather, it could be seen from twenty miles away. More often than not, mist enshrouded the island and visibility was markedly reduced. At such times, the value of the beacon to local shipping was incalculable.

A three man crew maintained the lamp at the top of the lighthouse. A rotation system ensured a change of personnel every fourteen days. Once a fortnight, a service vessel came from Breasclete and a new crew would be installed. Flannan Isle was not a place to stay for any length of time.

At twenty three metres in height, the lighthouse was - and is - an unremarkable structure. Built in 1899 on the largest of seven rocky outcrops, it is situated some fifteen miles west of the Isle of Lewis, on the outer fringes of the Hebrides.

On December 7th 1900, Head Keeper James Ducat arrived at the lighthouse to begin another tour of duty. His First Assistant, William Ross, had been taken ill and a local man, Donald Macarthur, had taken his place. Macarthur was an Occasional Keeper, who only filled in when regular crew members were unavailable. Second Assistant Thomas Marshall made up the trio.

Accompanying the three men on the relief vessel was Robert Muirhead, the Superintendent of Light Houses. Routine inspections were a part of his brief and Muirhead always liked to keep in close touch with the men under his supervision.

The Superintendent spent some time on the island, reassuring himself that everything was running smoothly. He had a brief discussion with the Head Keeper concerning improvements in monitoring, then bade him and the others farewell.

He shook each man by the hand as he departed the island. The Superintendent was the last person to see any of them alive.

During the following week, as was standard practise, the island was kept under periodic observation from land. A telescope would be trained on Flannan Isle at regular intervals. In case of emergency, the lighthouse Keepers could hoist an appropriate flag and assistance would be sent out to them. The lighthouse was often obscured by mist, however, and there was no guarantee that the signal would be seen. It was this very problem that Ducat and Muirhead had been discussing on the 7th December.

During the two weeks thereafter, a heavy mist enveloped the island. The lighthouse would not be visible again from land until 29th December.

The light from the lamp was easier to make out. Night observations were also a matter of routine. The lamp was visible on the 7th December, but was obscured by bad weather on the following four evenings. It was seen again on the 12th December.

After that, it was not visible for over a fortnight.

On the 15th December, the SS Archtor was in the vicinity of the island. At close to midnight, Captain Holman looked out from the deck of the steamer, expecting to catch a glimpse of the light from Flannan Isle, as per usual. Holman was close enough to the island and the weather sufficiently moderate for him to be certain to see it. But no light was visible.

The relief vessel from Breasclete did not arrive at Flannan Island on 21st December. A run of particularly bad weather had delayed the SS Hesperus and it was unable to reach the lighthouse until noon on Boxing Day, five days later.

As a matter of protocol, the lighthouse crew were expected to assist the incoming men, who would row from the Hesperus in a smaller boat to land on the island. A flag was usually flown to show that the incumbent crew had spotted the relief vessel and the men themselves would come out to greet the new arrivals. On this occasion, however, as the Hesperus drew close to the island, there was no flag flying and the lighthouse crew were nowhere to be seen. Captain Harvie, on board the Hesperus, gave orders to sound the siren.

There was no response.

The steam whistle was also blown, to similar lack of effect. The boat would simply have to land at Flannan Isle without the usual assistance. Joseph Moore, the Third Assistant Keeper, jumped onto the landing craft alongside the Hesperus’ Second Mate, McCormack and together they rowed ashore. With nobody to assist them from the landward side, it was a difficult job to pull up the boat. Moore had to jump ashore himself to grab the mooring rope and throw it aboard. As McCormack secured the launch, Moore went up to check on the Station.

The outer door to the lighthouse was locked. Moore had a set of keys. He unlocked the building and went inside.

The place was deserted. There was no sign of Ducat, Marshall or Macarthur. The clock on the inner wall had stopped. There was no fire in the grate and all the beds were empty. A meal had been prepared but was uneaten.

Moore hurried back to the launch. Breathlessly, he explained to McCormack that the crew were missing. The Second Mate joined him ashore and together the two men mounted a thorough search of the Island.

The original crew were not there. They had simply disappeared.

Moore and McCormack returned to the Hesperus and gave Captain Harvie the bad news. He instructed the Third Assistant to return to the Island with three others to take temporary charge of the lighthouse. Meantime, the Hesperus would return to Breasclete to inform the relevant authorities.

A telegram was sent by Harvie to the Secretary of the Northern Lighthouse Commissioners later that same day, informing them of the disappearance.

On Flannan Isle, Joseph Moore and the others made an even more rigorous search of the lighthouse and a picture of events soon began to emerge. As far as they could make out, everything had been running smoothly on the island until the afternoon of the 15th December. Accurate record keeping was mandatory for all lighthouse crew and the Head Keeper, Ducat, had conscientiously compiled reports up until the 13th. Draft entries for the 14th and 15th December had been written up on a slate. There had been a storm on the 14th, according to the draft, but by the next morning it had blown itself out. There was no indication of any further problems.

Whatever had happened to the three men, it had happened to them that afternoon.

Superintendent Muirhead joined the others at Flannan Isle on 29th December.

His official report is the most detailed account of the state of the island at that time.

The storm on the night of the 14th had clearly caused substantial damage. The jetty was warped and the railings were clearly battered. A store containing mooring ropes and crane handles had been washed away. The ropes from the box had become entangled on a temporary crane some seventy feet above the normal level of the sea.

Muirhead concluded that the men had left the lighthouse in order to secure this store against the storm. They had taken wet weather clothing and locked the outer door behind them. Then, Muirhead believed, they had either been blown off the edge of the rocks or - more likely - an unexpectedly large wave had swept over the top of them and dragged them out to sea. The first theory could be discounted, as the wind that day had been in a Westerly (uphill) direction. It was Muirhead’s conclusion, therefore, that a freak wave - referred to in his report as a roller - was ultimately responsible for the men’s disappearance.

The sea had claimed them and nothing could have been done to prevent it.

A new crew was installed on Flannan Isle and efforts were made to increase the effectiveness of daily monitoring.

But the memory of the disappearance lived on.

In 1912, Wilfrid Gibson published his famous poem, Flannan Isle. The piece lacked historical accuracy, but it created a disturbing sense of danger and uncertainty. In many ways, it is this work, rather than the actual events, which captured the imagination of the public. It has inspired music and fiction¹, and the inevitable crackpot theories. Aliens, mermaids and sea monsters have all been postulated as alternative explanations for the disappearance.

But no-one seriously disputes the findings of Superintendent Muirhead.

It was not aliens or sea monsters that killed the unfortunate Keepers of Flannan Island.

It was the Atlantic Ocean.