WHAT happened to Seajewel (IMO: 9388807) wasn’t a one-off. With four attacks on tankers in recent months, we may well be looking at what one marine underwriter this week described as “a pattern of deliberate action”.

Responsibility is unclear. But the common denominator among the vessels involved is that they have lifted crude at Russian ports in the last year or so.

Russian oil exports are, of course, subject to stringent sanctions from the West. Even the nascent love-in between presidents Trump and Putin has not to date seen any mention of them being lifted any time soon.

Yet it remains entirely legitimate to carry Russian crude so long as it is compliant with the $60 a barrel price cap. It is also permissible to lift crude produced by former constituents of the Soviet Union, such as Kazakhstan, which are often still handled at Russian terminals.

Such are the kind of entirely lawful and ethical fixtures undertaken by Thenamaris aframax Seajewel, which remains alongside at Savona, as the Italian authorities investigate what are officially described as ‘anomalies’ in offloading operations last weekend.

According to local media reports, the crew heard a loud bang during discharge, followed by an ingress of water. A second loud bang came 20 minutes later.

Divers subsequently inspected the underside of the ship and found a hole of about one metre in length. The hull plates were bent inwards, which is consistent with external force.

Other possibilities remain, including machinery failure. But from what has emerged so far, the indications point to nefarious action.

Officialdom the world over has a natural tendency to downplay this kind of thing, in the arguably justifiable interests of averting alarm.

Older readers may remember an explosion on or near Mitsui OSK Lines-owned VLCC M.Star (IMO: 9515436) in the Strait of Hormuz in 2010.

The first reaction for many was to regard this as a suicide speedboat assault mounted by Islamists, emulating the tactics deployed by al Qaeda against American destroyer USS Cole in Aden in 2000.

But the United Arab Emirates urged everybody not to jump to conclusions, insisting that the casualty may well have been the result of a freak wave following an earthquake.

Other potential causes canvassed included an old mine left over from the Iran-Iraq war of 1980-88, or a container lost in a stack collapse, or even a whale strike.

Not until four months later, when the story was pretty much old news, was terrorist involvement finally confirmed.

Some years later, a Lloyd’s List journalist dutifully attending a dreary industry wine-and-canapes event got talking to one of the scientific experts who had been involved in the investigation.

It seems the issue was never in the slightest doubt. But the decision had been taken at the top to damp speculation down as far as practicable, in order to avoid destabilising the tanker trade in the region.

We know already that what happened to Seajewel was not a one-off. Another Thenamaris aframax, Seacharm, was also damaged by a blast off the Turkish Mediterranean port of Ceyhan in January.

There have been two other suspect blasts, although details are somewhat sketchy.

In the sanguine assessment of marine underwriters, who do after all have skin in the game, the situation so far has not reached a pitch at which it can be regarded as a systematic threat. War risk premiums remain unchanged for the time being.

The knowledge that such perils will be met with an insurance payout will come as some comfort for shipowners. But the tankers and the seafarers that serve on them are effectively sitting ducks, with no viable means of protecting themselves.

Meanwhile, we are faced with the unhappy prospect that an organised campaign is being mounted against the tanker sector, by persons unknown and for reasons unknown.

There is no-one to negotiate with; no grievances have been stated, no known attempts made to extort money by way of some protection racket.

But whatever the ostensible justification, these events are literally criminal. So far, there have been no reported deaths, injuries, or pollution. The fear is that luck might not hold indefinitely.