The boarding and holding of the tanker Grace 1 off Gibraltar, while allegedly carrying Iranian crude oil to Syria, in breach of European Union sanctions regime, was clearly going to provoke a response. Indeed, the Tehran regime clearly articulated the fact that they would do something in retaliation.

Having already carried out a number of attacks on international tankers in and around the strait of Hormuz, a week ago, an attempt was made to take a British-flag registered ship, the BP British Heritage. It was only thwarted by the close presence of HMS Montrose.

The UK issued a warning to British-registered shipping to avoid the area and raised the threat level. But this was not good enough. We should have enacted control of shipping procedures, directing ships to assemble in safe areas and then taken them through in convoy.

Even with only one major warship in the Gulf this could have been done until reinforcements arrived – although the Royal Navy is disgracefully short of ships.

Instead, we seem to have been oblivious to the fact that one of our ships was steaming on to become a hostage to fortune. It now transpires that Iranian forces have taken control of the British-flagged Stena Impero and its 23-strong crew, while the tanker was in Omani waters.

So, where do we go now?

The Grace 1 is held off Gibraltar for another 30 days and I do not believe Jeremy Hunt, the foreign secretary, is legally allowed to release the ship to Iran, even if the Iranians do promise the ship will not go to Syria, whatever that promise would be worth.

Facebook Twitter Pinterest The oil tanker Stena Impero was seized by Iran. Photograph: Contributor#072019/Getty Images

So, any UK-flagged ship passing through the strait of Hormuz, and indeed in other areas around the Saudi Arabian peninsula, will be at risk. While our aim is to de-escalate the tension we must not confuse that with the first duty of any nation – to protect itself and its people. Therefore until some allied arrangement for escorting ships through the strait is set up, we should escort small groups of UK-flagged ships with the one escort we have available.

We should aim to have four escort ships in the region – what an indictment of the cuts to our surface fleet by successive governments.

It is important that we enforce the right of free passage which is so vital to the free flow of trade around the globe. A military response against Iran is not appropriate and, in any case, is beyond the capability of our armed forces acting alone.

But we should make it clear to the Iranians that, while up until now we have been trying to talk to Washington about easing sanctions, we will side with the US and strengthen sanctions unless Iran releases our ship and its crew.

There are very real risks of a miscalculation or some foolhardy action leading to a war. And, despite what some people think, should a war start there is no way the UK could avoid being fully involved on the US side.

Some powerful groups in Israel, Saudi Arabia and the United States want war and think a precision strike against key parts of Iran’s military capability would lead to regime change. They are wrong. It would lead to an open-ended war with catastrophic consequences across the region and the globe.

The other unfortunate outcome of Donald Trump’s decision to withdraw from the Joint Comprehensive Plan of Action (JCPOA), better known as the Iran nuclear deal, is that Iran has restarted uranium enrichment. The last thing anyone wants is a renewed nuclear race in the region. Israel would again feel a need to strike in order to stop Iran acquiring nuclear weapons. It came within days of carrying out such an attack prior to the JCPOA deal.

This crisis has developed as the eyes of our political establishment have been focused on the election of a new Tory leader and a new occupant of No 10. Whoever the next prime minister is, he is going to face a major international crisis as soon as he is in post. It cannot be ignored because of Brexit.

•Admiral Lord West is a former First Sea Lord and Chief of Naval Staff