In one of the Navy's biggest ever seizures, HMS Grafton tracked the drug runners' boat off Venezuela.

Spy planes and the warship closed in on the suspicious boat after a tip-off from the US drugs agency.

British, American and Dutch aircraft were involved in the sea search for the boat, the Genesis, but it was the British frigate which pinpointed its location.

It may be just a small dent to their empires but it will make a difference

Lt Cmdr Walker

After questioning the boat's crew by radio and seeking permission from the Venezuelan government to board it, a detachment of US Coastguards assigned to the Grafton seized the Genesis.

After a lengthy search a secret compartment was uncovered containing 14 bails, around 750kg, of high-grade cocaine.

The naval officers knew the boat's crew had to be hiding something because they had no ice or fish on board.

Scuttle plan

"After measurements were taken, we discovered a compartment inside the boat's hidden wall, and the cocaine bails inside," logistics officer Lieutenant Commander Donald Walker told the Mirror newspaper.

"That was quite a sight."

Lt Cmdr Walker described how the crew tried to scuttle the boat by flicking a hidden switch.

"It was a long, difficult and tense operation, but very rewarding," he told the newspaper.

Drug gangs

The drugs and crew were brought aboard the British warship.

Both will be handed over to the Venezuelan authorities when the ship docks on Thursday.

It is the biggest haul of illicit drugs by a British warship since 1999, when another vessel recovered cocaine worth £1bn.

South American drug gangs use the Caribbean islands as staging posts on the way to North America and Europe.

The Royal Navy believes its efforts are making this harder.

Lt Cmdr Walker told the Mirror: "It may be just a small dent to their empires but it will make a difference."