Daniel Hazelton, 30, and Adam Taylor, 28, both of Rickinghall, and Thomas Hazelton, 26, and Peter Johnson, 42, both of Stanton, near Bury St Edmunds, died on January 21, 2011.
The deaths occurred at the premises of Claxton Engineering in Great Yarmouth where a high pressure test bay for offshore components was being constructed.
During the first day of the inquest the jury heard that the four men were working inside the cage below ground level in an excavation reported to be the “length of a tennis court”
The steel cage was to reinforce the concrete base of a unit to test offshore pipes, forming part of a £1.5m new test facility.
John Elvin, for HSE, described the moment that the cage collapsed with the men inside as a “racking movement” best likened to a “collapsing picnic table”.
He said access to the trench was via a ladder and that part of the side wall had collapsed and water needed to be pumped out. The area was described as “marsh land” and had needed piling work earlier in the build.
Mark Aylen, procurement manager for Claxton Engineering, said he had raised concerns about the men working inside the metal cage. He said he had seen one man “squeezing” through and was concerned it would take him a long time to get out in the event of an emergency. Project builders Encompass had assured him the groundwork sub-contractors Hazegood knew how to work properly.
Mr Aylen admitted there had been “no formal handover” when the previous Claxton project manager left for Dubai in October 2010. He left risk assessment matters to Encompass and did not know Hazegood had been employed as sub-contractors until the day work began.
Operation Madera, headed jointly by Norfolk police and HSE, ran for 13 months and the file rested with the Crown Prosecution Service (CPS) in London for around a year. In February 2013 CPS ruled charges of individual gross negligence or of corporate manslaughter would not be brought.
DCI Andy Guy, of the joint Norfolk and Suffolk Major Investigations Team, said he had challenged this decision but the result came back the same. He expressed concern that the case had been “passed between lawyers three times”. He added:
“I just wanted a separate opinion as after a 13-month investigation I understood things a certain way. I just wanted to make sure everything was clearly understood.”
He said the CPS must have deemed there to be no realistic prospect of securing a conviction.
The HSE has yet to reveal whether a proceedings will be taken under health and safety legislation.
Senior coroner Jacqueline Lake is set to hear further evidence as the inquest continues.