Belgium could build island over abandoned poison gas grenades

Bulwark could protect against rising sea levels and 35,000 tonnes of first world war weaponry on seabed

For almost 100 years 35,000 tonnes of poison gas grenades, abandoned by the fleeing Germans around first world war battlefields, have lain in steel barrels on the seabed less than a kilometre from the Belgian coastline.

A convoy of small boats dumped the cargo into the North Sea over a period of six months in 1919 when unloading it into the world's oceans was thought to be the best way to protect people from exposure to the toxic material.