The Macron-Starmer joint statement published on GOV.UK on 17 April gave the Hormuz coalition at 51 nations, not the 40 reported in the first wave of coverage 1. The 27% upward correction is a primary-source fact from the UK Government's own publication platform that has not yet displaced the 40-nation figure in most wire copy. The statement characterises the mission as "strictly defensive" and makes deployment contingent on "a sustainable ceasefire agreement".
Italy, France, the UK and Germany were named; the Gulf Cooperation Council (GCC) and Saudi Arabia were not. The United States was not in the room and will be "briefed on the outcome". Military chiefs from the 51-nation coalition will meet at Northwood, the UK Permanent Joint Headquarters in north-west London, in the week of 20 April to draft rules of engagement . Over a dozen countries have offered assets, logistics or finance.
The deployment trigger binds the mission to whichever architecture emerges from the 22 April ceasefire expiry question, which is the same ceasefire Tehran is currently running a 24-hour open-and-close cycle on. Rules of engagement written at Northwood by UK and French officers will reflect European legal preferences drawn from UNCLOS transit-passage doctrine, the same legal spine the European Union used when it rejected Trump's Hormuz toll joint venture earlier in the war. In international maritime law, the first credible multilateral text usually holds; any later US arrangement will either reach into this framework or argue round it.
