There's no more important a decision a prime minister can make than to send British forces into action. I never thought I would be part of another cabinet discussing this, still less watch another prime minister weighing up such a decision.
But that is where I was last week. And I could see what a careful, thorough and strong approach Rishi Sunak was taking. Every relevant consideration was carefully weighed. Every minister forensically quizzed that their department had done all the necessary work. But in the end, the cabinet agreed we had no choice but to act.
The freedom of navigation really matters. Since Nov 19, there have been 26 attacks on shipping in the Red Sea. Not acting would be accepting that illegal and unacceptable Houthi's attacks could virtually shut a vital sea lane with relative impunity.
We have to recognise the vital connection between events overseas and our lives at home. Experience in recent years makes it absolutely clear: the actions of malign actors abroad matter to us at home.
The Red Sea is one of the major arteries of international trade: some 15 per cent of the world's shipping passes through the narrow strait dividing Africa from Asia. If the Houthis deny this passage to ships, vital supply chains are threatened and prices will go up in Britain and across the globe.
As a direct result of their attacks, the International Chamber of Shipping says 20 per cent of the world's container ships are already using the much longer route around the southern tip of Africa instead.
The global coalition to protect shipping in the Red Sea has been growing. And we have been involved from the start, with the Royal Navy taking an active part in Operation Prosperity Guardian to help keep this vital sea lane open. But the attacks have continued.
The prime minister carefully considered a request from the United States to assist with limited and targeted military action. After examining all the arguments, including legal advice, and after consulting cabinet colleagues and our military and intelligence experts, he confirmed that we should take part.
Fundamentally, when we agree with our allies on the need to act and have the capabilities to help, it is right that we should do so. We are a trading nation. Keeping sea lanes open is a vital national interest.
As prime minister, I was involved in the long-running campaign to stamp out attacks by Somali pirates in this same stretch of water. It was right to take action against those trying to hijack ships then. It is right to take action today. As with Somali pirates, we have not acted alone.
We have not rushed into these strikes. As well as assembling and deploying a naval task force, we have given warning after warning. A coalition of 44 countries spoke out before Christmas. The United Nations Security Council has demanded the attacks should cease.
I spoke directly to the foreign minister of Iran, the Houthis' major ally. We left them in no doubt. Attacks against merchant and commercial shipping are completely unacceptable. They had to stop.
The Houthis chose to escalate. On Jan 9, they launched 21 drones and missiles at a British ship, HMS Diamond, and those of our US allies, in one of their biggest attacks to date.
Military action should always be a last resort. And it certainly was in this case. For almost two months we endured these attacks without responding directly. This did not prevent targeting of our forces, did not deter attacks on traders in the Red Sea, and, therefore did not effectively defend the principle of freedom of navigation.
Our strikes were necessary, proportionate and lawful. The Royal Air Force took particular care to avoid civilian casualties — in sharp contrast to how Houthi drones have threatened the lives of civilians of all nationalities working in the shipping industry.
The Houthi contention that this is all about Israel and Gaza is nonsense. They've attacked ships from countries all over the world.
Our joint action will have gone some way to degrade Houthi capabilities built up with Iranian backing. We targeted sites from which we know their attacks were launched.
We have sent an unambiguous message: what the Houthis are doing is wrong, and we are determined to put a stop to it. We will work with allies. We will always defend the freedom of navigation. And, crucially, we will be prepared to back words with actions.
* The writer is foreign secretary of the United Kingdom