The declared IRA's aim was to disrupt the maritime traffic out and from the Londonderry Port, on the east bank of the Lough. They also intended to force British and Irish authorities to deploy security guards on board the merchant ships
On the British side, the Bird class patrol boats HMS Cygnet and HMS Kingfisher were already assigned by the Royal Navy to protect the waterways of the province. Their mission was to prevent the smuggling of weapons from the Republic.
The Nellie M was a coaster ship of 782 BRT, launched in 1972 at Yorkshire. She was owned by S. William Coe & Co. Ltd. of Liverpool at the time of the attack, which took place on 6 February 1981. The vessel was at anchor barely from the Republic’s shore, awaiting for proceeding up the river. The coal ship had departed from Liverpool with a cargo valued at £ 1 million.
A team of 12 IRA volunteers, meanwhile, had hijacked a pilot boat at a pier on Moville, on the northwest bank of the inlet. Five of the group remained watching on shore, while another seven members of the ASU, carrying two high explosive charges, forced the skipper to take them to the British coal ship. Once on board, the cell informed her captain about their intentions and ordered him to gather the crew and to get his men into the lifeboat. Four volunteers supervised the evacuation. At the same time, three other volunteers planted the charges in the engine room. The hijacked motor launch then took in tow the lifeboat, leaving her adrift close to the eastern shore, and headed back for Moville. As the lifeboat reached the beach, the first explosion shook the Nellie M. Huge flames, visible from several miles away, engulfed her bridge. A second blast, some hours later, blew up the bulkheads and the ship began to sink. The morning after, her stern was submerged. The hull was raised in 1982.
The next year, the IRA was able to repeat the same operation against another British coal ship, the St. Bedan, bound from Glasgow to Derry. The 1,250 BRT Bedan, built in Clyde and also launched in 1972, was owned by J & A Gardner & Co. Ltd. of Glasgow. On February 23 1982, the ship was at anchor off Derry, awaiting the tide to proceed upstream.
This time the IRA boarding party was composed of 12 members. The attack was again launched from the pilot boat based at Moville, and after the explosions, the cargo vessel sank on her starboard side in some 15 meters of water. She was raised and scrapped by November 1982. The lifeboat with the crewmembers was towed in the same way that in the case of Nellie M.
One of the unexpected consequences triggered by the bombings was the debate in the Oireachtas about the dispute with the United Kingdom on the legal jurisdiction over the waterways in Northern Ireland. Indeed, the salvage of the Nellie M was conducted by an Irish company, and her wreckage was sold to an Irish ship owner, who refurbished the ship under the name of Ellie. The coal ship was subsequently bought by several companies. She was lengthened by seven meters and renamed Trimix . Since 2000 she is managed by a Columbian company after being rechristened Dove. The St. Bedan was instead declared a constructive loss and scrapped at Liverpool.
The IRA discontinued these attacks; this fact strongly suggests that the authorities redoubled their vigilance on the Irish side of the Lough, from where the seaborne assaults were launched. These measures apparently prevented further activity. A bigger naval target was hit by the IRA several years later (1990), when a number of volunteers managed to board the RFA Fort Victoria at anchor near Belfast, shortly after her launching. They planted two large bombs in her engine room. One of the devices exploded, damaging her considerably; the second one was successfully defused.