Offshore Firm Fined £287,000 After North Sea Rig Worker Fell Through Dislodged Grate Into Sea

An offshore drilling company has been fined more than £287,000 after a worker disappeared from the Valaris 121 rig in the North Sea and was later presumed dead following a major safety investigation into safety failures during a rig transit operation.

Ensco Offshore UK Limited admitted breaching UK health and safety laws after investigators concluded that offshore worker Jason Thomas fell through a displaced deck grating and into the sea while the jack-up rig was being towed to Dundee for maintenance in January 2023.

Jason Thomas, 50, from South Wales, was working aboard the Valaris 121 rig, about 100 miles south-east of Aberdeen, on 22 January 2023.

The rig was under tow to Dundee when weather conditions worsened, with winds exceeding 30 mph and waves rising above five metres.

Mr Thomas, who had around 16 years of offshore experience, was supervising the deck crew during his shift. Earlier that day, he carried out water integrity checks with another worker, with seawater reportedly coming over their boots.

At around 2.30pm, he was seen taking a break in a staff lounge. Around 15 minutes later, a mechanic entered carrying a lifebuoy that had broken loose from its holder on the main deck. Mr Thomas told him to leave it there and said he would “deal with it”.

He was last seen at about 3.05pm leaving the lounge carrying a cup of coffee and his mobile phone.

Around 4pm, another worker heard a loud noise outside. When he opened the door to deck 1, he found that a grating outside the airlock door had become displaced, leaving a large opening above the North Sea.

Repeated tannoy calls failed to locate Mr Thomas. HM Coastguard was contacted shortly before 9pm and launched a major search operation involving offshore vessels and aircraft. His body was never recovered.

His hard hat, gloves and radio were later found near the airlock door.

HSE investigators said the grating panel involved in the incident had not been secured in line with original equipment manufacturer specifications.

Later inspections also failed to verify the deployment of Hilti clips designed to stop deck gratings from lifting under stress.

The Valaris 121 is a jack-up offshore drilling rig designed to elevate above sea level on extendable legs while operating. During towing operations, however, the hull remains afloat and exposed to wave action.

HSE investigators concluded that wave forces generated during the transit created sufficient upward pressure to dislodge the improperly secured polymer grating.

The failed fixing system allowed the panel to lift free, creating an exposed opening above open water.

Following the incident, the company replaced polymer gratings across its fleet with galvanised steel systems.

The HSE said examinations at its Buxton scientific facility found no evidence of malicious interference or tool marks on the fastening system, ruling out sabotage.

At Aberdeen Sheriff’s Court on 18 May 2026, Ensco Offshore UK Limited pleaded guilty to breaching Sections 3(1) and 33(1)(a) of the Health and Safety at Work Act 1974.

The company was fined £267,000, while an additional victim surcharge brought the total financial penalty to £287,025.

HSE principal inspector Stephen Hanson Hall described the case as a “profound tragedy” that left a lasting impact on Thomas’s colleagues and family.

He said the investigation found that relatively simple risk-control measures during the rig move could likely have prevented the incident.

Thomas’s mother later obtained a presumed death certificate through the Welsh courts confirming he died on the day he disappeared. She died shortly after receiving the confirmation.

Reference: HSE Gov