“It’s a matter of time before a yacht gets taken,” the spokesman for EUNAVFOR, the EU coalition forces patrolling the Gulf of Aden told me when we met a fortnight ago.

“I’m afraid,” he added, “that the next time we talk it will be after one has been captured.”

Tragically, that proved prophetically true.

Last Friday, Quest, a 58ft US yacht belonging to Scott and Jean Adam was reported to be in the hands of pirates and yesterday it was reported that they and their two crew, fellow Americans Bob Riggle and Phyllis Macay, had all been killed during a gunfight on board.

Quest was reportedly being monitored by the US Navy, which sent three ships deployed in the area: the guided missile cruiser USS Sterett; guided-missle destroyer USS Bulkeley and the 1,123ft nuclear-powered aircraft carrier USS Enterprise.

US Central Command stated yesterday that negotiations with the pirates were underway when gunfire was heard. We understand that a disagreement had broken out on board between the pirates about whether to agree to a negotiated settlement and two pirates were killed as they squabbled.

The Marines responded and boarded the yacht, and reports say that two more two pirates were killed as they tried to gain control: one was shot; another died from knife wounds.

The official report states: ‘As [US Marines] responded to the gunfire, reaching and boarding the Quest, the forces discovered all four hostages had been shot by their captors. Despite immediate steps to provide lifesaving care, all four hostages ultimately died of their wounds.’

This dreadful and chilling incident unfortunately confirms the validity of military warnings reported in our current issue that a vast swathe of the Indian Ocean is a high risk, effectively no-go area.

Last month EUNAVFOR, the EU coalition anti-piracy force patrolling the Gulf of Aden contacted us to issue stern warnings about the risks cruising yachts and rallies were running on passage through the northern Indian Ocean.

The risk of piracy has spread across a huge area, they emphasised, as far east as the Laccadive Islands off India and down to the Maldives and even the Seychelles, where British sailors Paul and Rachel Chandler were taken in 2009.

They were so worried that they issued an open letter drawing attention to a high risk area stretching ‘from Suez in the North, 10°S and 78°E’.

We have shown the extent and distribution of pirate attacks in the map at the top.

‘We have become aware of a number of planned rallies that will transit through the High Risk Area in the Gulf of Aden and the Indian Ocean… The threat of piracy continues as their modus operandi and ability to operate at greater distances from the Somali coast evolves,’ it said.

‘The advice remains that yachts should avoid the area.’

The three rallies being referred to here, the Blue Water Rally, the Thailand to Turkey Rally and the Vasco da Gama Rally all modified their routes. The Blue Water Rally participants are currently following a more coastal route from India to Salalah in Oman and in carefully arranged convoys – they and we are obviously not giving details of this.

It was this rally that Scott and Jean Adam had chosen to join in Thailand in December, specifically to sail in company to the Mediterranean. They had received numerous safety and security briefings about the risks and suggested precautions, in writing and face to face.

As far as we can ascertain, their intention was to continue with the rally from Mumbai. But at some point, possibly the night before departure, Scott Adam changed his mind and decided to strike out straight for Salalah and go it alone.

You would think, wouldn’t you, that the odds of being spotted in such a vast area of water were low?

That they were captured so far out to sea, some 450 miles from their destination and hundreds of miles from the nearest coast, suggests that the danger EUNAVFOR has been spelling out, of pirates operating semi-permanently from captured cargo ships and large fishing boats, is now a serious and extensive menace.

As we report in our current issue, up to eight cargo vessels and even tankers are believed to be at large in the Indian Ocean, their crews held hostage and used as human shields.

These motherships are ideal bases from which to extend the scope of raids by fast skiffs and negotiations for ransom can continue as they operate.

Just as naval warships send out helicopters to increase their scope of surveillance, these pirate groups can send out skiffs on wide-ranging bounty-hunting missions.

It seems likely that the poor crew of Quest were spotted in this way.

The yacht is reported to have been boarded by 19 pirates, a very large and ultimately volatile group.

According to a briefing to ISAF by the Maritime Security Centre Horn of Africa in October, a typical pirate skiff (which, by the way, would be identical to hundreds or thousands of fishing vessels legitimately going about their innocent trade in these waters) is 30-40ft, with high-powered outboards.

The same report says that these pirates, the bottom layer of a huge pyramid of big business interests and syndicates based in Somalia, are ‘mostly young [and] they chew a locally made drug, khat, which keeps them in a constantly heightened state and makes their actions unpredictable’.

Typically, they are armed with rocket-propelled grenades and small arms. That seems to have been the case here, as there are reports that the pirates fired an RPG at one of the US warships, thankfully missing.

Why the crew of Quest chose to take this route we will never know. It must not have seemed to them like such a big chance to take.

But it underlines a sad and terrible fact: that a massive area of the Indian Ocean should be considered very dangerous indeed – far, far more so than was the case even last year.

The danger area now stretches from the Gulf of Aden down to the Seychelles, 650 miles south (this where Paul and Rachel Chandler were captured in 2009) but also east to the Maldives and Laccadive Islands, which are some 1,400 miles from Somalia.

That’s as far away as, say, Turkey or Libya is from London.

Unbelievably we are talking about a high risk area stretching over 1.4 million square nautical miles.

If I were contemplating a cruise back to Europe from the Far East, I wouldn’t even think of the Red Sea, which can be a pretty horrible sailing experience in itself. I’d be looking at taking the longer route round the Cape of Good Hope, or even shipping my boat back.

But both of those options have some potentially big disadvantages.

We look in depth at the problem of piracy and the background to it in our April issue, and at the implications for a world cruise in our May issue.