Dusk is falling in the Gulf of Aden; the sea is oily flat, and the day's heat still beats upward from the deck. The big freighter's small crew, perhaps Indian and Filipino with a few European officers, are nervous. Jumpy. They have every reason to be.

Suddenly the roaring of outboard engines is all around them. They run for the fire-hoses to repel boarders, but freeze as they are covered by AK47 rifles. Within minutes the ship is a hostage, steering for a lawless harbour. All they can do is hope that their owner pays up; for once again, Western commerce and international seafaring have been humiliated by a ragtag navy of Somali pirates. It happens weekly. The last one was a Greek chemical tanker on Friday: the predators threaten to blow it up unless they get their money.

Who is to stop them? Somalia, the world's most neglected tragedy, has been ungoverned for years. The UN Security Council is “drafting a resolution” and the EU is cautiouslly setting up a “Mission” against piracy that will - we heard only yesterday - have its headquarters aboard the British frigate HMS Northumberland, which, after years of pathetic indecision, the Ministry of Defence has finally agreed to deploy.

International action against this growing pest and danger has been remarkably feeble. The French, rightly losing patience, at least carried out two commando rescue raids. Most nations just pay up. As for us, the Royal Navy that once cleared the seas of pirates (and before that, of slave ships) has until this meagre deployment been made powerless.

Not long ago officers were explicitly advised not to capture Somali pirates in case they claim asylum, nor to send them home in case their crazy fatherland violated their human rights. Brows were furrowed in leisurely debate over whether gangsterism is technically piracy when it takes place in Somali territorial waters. But all this grows academic, since the Royal Navy has been cut savagely in recent years anyway, and is currently crippled by supplying half the manpower and airpower for landlocked Afghanistan.

The situation could become as urgent as any banking crisis. For all the ignorant sea-blindness of this island nation, the cold fact is that without sea trade we would have little food, fuel, or goods. The Gulf of Aden is a vital pinch-point in sea routes from the East, and a scan of the world's maritime media from India to Argentina confirms that pirate attacks have doubled in a year: 67 so far. The marauders are ever better equipped - radios, speedboats, rocket-propelled grenades. Vast ransoms are paid, and the pirates are sophisticated enough to know insurance values. Of the 26 ships successfully hijacked this year 11 (and 200 crew ) are currently held. One is the Faina, a Ukrainian freighter loaded with Russian heavy weaponry. The marauders' managers are said to have links to fundamentalist movements. As the Americans say, go figure: once al-Qaeda notices that you can cripple the West by disrupting the sea routes, a lot could happen fast. About 22,000 shipping movements pass Somalia every year, including tankers bearing 4 per cent of the world's oil needs. Even a fractional disruption would hit prices, supplies and global stability.

Until two days ago the UK was uniformly feeble in its response. A Foreign Office spokesman has bleated: “There are issues about human rights... the main thing is to ensure any incident is resolved peacefully.” Tell that to a gangster with an AK-47 and a headful of khat. The senior British RN commander in the Gulf, Keith Winstanley, suggests rather desperately that merchant ships should carry armed mercenaries and mounted machineguns to defend themselves.

Insurance companies respond in the only way they know, which is to ramp up premiums. What has finally spooked our Government into its small gesture now is that some shipowners, ever pragmatic, have simply opted to go the long way round via Cape Town. An extra 6,853 miles each way by my reckoning: work out what that'll do to prices and the environment.

Well, things are stirring. Russia has said it will co-operate. Some US warships are being diverted. We have, after majestic delays, sent one ship. But it is not a robust response yet, not one to convince sea jackals that the game is not worth it. The feebleness has been breathtaking: three years ago the Ministry of Defence said the UK “vigorously opposes acts of piracy” but would not divulge its intentions “due to security concerns”. When the International Maritime Bureau made a direct request for RN intervention, a promise was uttered that “if” there were warships in the area they would “help to deal with the problem”. Two full years later, when HMS Campbeltown was in the Gulf, the Ministry said evasively: “We are aware of piracy issues... but we have to take a long-term view on our resources” adding that it had “strategic decisions” to make.

Indeed it does. Our force of destroyers and frigates has - in ten years - shrunk from 35 to 22 despite promises that it would not slip below 25. The number of smaller vessels, minehunters, decreases annually (they could be handy in this work). We mothball ships or flog them to Estonia; the navy budget faces cuts of 20 per cent over ten years. Its air cover is crippled, with one lot of planes gone and the next not ready.

I do not denigrate the Royal Navy: far from it. Senior officers are itching to deal with the dangerously underrated problem of Somali waters. Deterrence, they say, would not be too difficult with trained crews, fast ships and a clear mandate. But what the wet-lettuce attitude of government demonstrates is that naval power - one of the most useful, flexible, historically successful and often peaceable arms of the State - continues to be run down with cavalier disregard for our total dependence on sea trade.

Even if the UN and Europe cobble up a solution to this crisis, that problem of British naval erosion will not quickly go away.

One of the worries that keep Admirals awake is that the smaller the Navy grows, the more humiliated and sidelined, the more training and tradition suffer. Government may secretly nurse some half-baked idea that mothballed ships are like Green Goddess fire engines, easy to haul out in an emergency. But if the Royal Navy goes on shrinking and being raided for manpower in Afghanistan, there won't be anyone fit to man them. Something precious will be lost, and our islands lie more open to blackmail and danger than at any time since Henry VIII.

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