BRUSSELS — Many Britons see their country as a brave galleon, banners waving, cannons firing, trumpets blaring. That is how the country’s voluble foreign secretary, Boris Johnson, likes to describe it.

But Britain is now but a modest-size ship on the global ocean. Having voted to leave the European Union, it is unmoored, heading to nowhere, while on deck, fire has broken out and the captain — poor Theresa May — is lashed to the mast, without the authority to decide whether to turn to port or to starboard, let alone do what one imagines she knows would be best, which is to turn around and head back to shore.

I’ve lived and worked for nine years in Britain, first during the Thatcher years and then again for the last four politically chaotic ones. While much poorer in the 1980s, Britain mattered internationally. Now, with Brexit, it seems to be embracing an introverted irrelevance.

The ambitious Mr. Johnson was crucial to the victory of Brexit in the June 2016 referendum. But for many, the blusterings of Boris have lost their charm. The “great ship” he loves to cite is a nationalist fantasy, a remnant of Britain’s persistent post-imperial confusion about its proper place in the world, hanging on to expensive symbols like a nuclear deterrent while its once glorious navy is often incapable of patrolling its own coastline.