Authorities in Gibraltar may have a big headache brewing with the seized VLCC Grace 1.

Stephen Askins, a partner at London law firm Tatham & Co, said the UK territory has been quick to say that the [Iranian] crude on board was bound for Syria, which suggests that the vessel may yet be stuck for the full 90 days allowed under its legislation.

This then opens up the question of the viability of any insurance, he added.

Panama de-flagged the ship in May. Shipping databases list the insurer as the Swedish Club, but the club declined to comment on whether this was still the case.

"If Panama de-registered the vessel some months ago it would be a surprise if there is a P&I Club blue card in place," Askins said.

Gibraltar is "potentially sitting on an uninsured (and possibly unseaworthy) tanker with a significant quantity of crude loaded on board."

He added: "Much of the security effort is aimed at the shipping off Iran but if they cannot get their ship back there is a scenario (logistically challenging as it is) that they take direct action against the ship itself.

"A serious pollution incident off Gibraltar does not bear thinking about and would raise interesting issues about liability and who would bear responsibility for any clean-up costs. It would make the Prestige incident and subsequent political fall-out look minor in comparison."

Askins said: "It must be assumed that the security around the ship is good but if the ship does look as if it is there for some time, it may be in Spain's interest if they were to offer somewhere to offload the cargo in the meantime."

Charter questions

Askins also said Iranian threats against UK shipping give rise to serious questions as to whether the level of risk and danger as set out in clauses such as Conwartime can now trigger the right to refuse orders to transit the Strait of Hormuz, particularly by owners with direct connection to the US or UK.

"The danger to shipping is a real one as demonstrated by recent attacks and whilst the risk of further attack may be relatively small the consequences of being seized are significant," he added.

"As ever the answer lies in a full analysis of the charter party wording."