Relatives lay wreaths on Saturday to remember two teenage brothers and their workmate killed in a freak sewer accident in London’s East End when they were poisoned by hydrogen sulphide gas.

David Richardson, 19, and brother Paul, 17, died in 1990 with 32-year-old Steve Hammond while working in the sewer below Watney Market, off the Commercial Road. Only a fourth member of the work party, 20-year-old Paul Barker, survived.

The boys’ sister, Carol Hammond, is leading the mourners in a minute’s silence at 12.30pm, which will also remember Stephen Reilly who was killed in another accident the year before, on the giant Canary Wharf construction site.

The sewer tragedy led to protests in east London after the construction company involved was fined just �50,000.

At the time, the boys’ father Derek Richardson called for criminal charges. It led to the national Construction Safety Campaign which fought to get Corporate Manslaughter legislation passed in 2007.

The organisation is also holding a national remembrance service at Tower Hill on Saturday, at 10.30am, in addition to the Watney remembrance two hours later, as part of its annual Safety Day commemoration for all workers killed in industrial accidents in Britain.