The Widow of a South West Water employee who drowned in a sewage treatment tank in Falmouth has criticised the company's lone worker policy.

Robert Geach, 54, a waste water operative with 24 years experience, died in a final settlement tank while working alone at the company's site near Falmouth Docks on December 30, 2013, and was discovered by an on-call colleague more than three hours after he was expected home.

Jurors heard a statement from his wife of more than 30 years, Sylvia, who said he went to work "as normal" at 8am and was expected back at 4pm or 4.30pm.

However, as she knew there had been some trouble with one of the tanks two days previously she was not surprised that he was late returning home, she didn't hear anything from him during the day, and even when she received a call from South West Water's Exeter office at 6pm she didn't think anything of it because she knew that telephone reception at the works could be patchy.

Mrs Geach said she didn't think the lone worker policy was "suitable for people working in isolated or particularly dangerous locations," and that there "can be a delay in finding out someone is in trouble and sending someone out [to look]."

On the first day of the five day hearing, the jury was shown a video recreating the task Mr Geach is believed to have been carrying out when he fell in the tank, which involved opening a service hatch on top of the tank and reaching in to make adjustments.

They heard from pathologist Dr Hugh Jones, who gave the cause of death as drowning and said Mr Geach would have been alive when he entered the water, adding that there was no evidence of a cardiac arrest.

Dr Jones described Mr Geach as "a sizeable chap" and said he was not "100 per cent satisfied" that he could have got down the hatch.

Also giving evidence was Mr Geach's colleague Terry Gorniak, who was an on-call on December 30 when he received a call at 6.22pm while at his home in Redruth, telling him the lone worker alarm was going off.

He arrived at the site and found Mr Geach's phone and personal effects in the site office, and checked all the other buildings before making his way to the tank, one of 18 at the works.

Walking up the steps, he saw Mr Geach's hard hat and gas monitor near the hatch, and looked in to see his colleague face down in the water.

As Mr Geach was out of reach, he called 999 and ran to get help from, Julian Vabo, a security guard at the nearby Pendennis Shipyard, and between them the two men pulled Mr Geach from the water.

Answering questions, Mr Gorniak said the hatch would have been wide enough for Mr Geach to fall in, as he and Mr Vabo "didn't have to struggle getting him out," and added that there was no reason for him to get into the tank, but once inside there was no ladder by which he could get out.

He told the coroner that the lone worker system was an automated system which called a worker at a pre-set time, and raised the alarm if there was no response, adding that it was "not uncommon" for the alarm to go off due to poor mobile coverage making it difficult to contact operatives; "maybe once a week."

The jury also heard that there had been no findings from a toxicology report by Dr Stephen Morley.

On Monday afternoon the jurors and interested parties visited the scene of Mr Geach's death, and more evidence will be heard onTuesday and Wednesday before coroner Dr Emma Carlyon begins her summing up on Thursday.