Britain's Royal Navy seized its largest ever cocaine haul in a drugs bust off the coast of South America.The Ministry of Defence announced today that the frigate HMS Iron Duke found a five and a half tonne stash, with a street value of 240 million pounds, smuggled on board an old fishing vessel.<br/> The Royal Navy crew spent more than 24 hours scouring the MV Cristal, eventually smashing through a concrete floor with sledgehammers and unbolting steel panels to uncover the hidden cargo.This is the largest seizure of cocaine in Royal Navy history, and is a very significant victory in the continuing fight against illegal drugs.