All the clocks on the Royal Yacht Britannia, now moored beside the blue car park at Ocean Terminal shopping centre in Leith, near Edinburgh, show the same time: 3.01pm. That was the moment on 11 December 1997 that the Queen stepped off the ship for the last time, famously weeping as a Royal Navy band piped a farewell to the soon-to-be-mothballed vessel.

No one, not even the Queen herself, can seriously have expected ever to see another royal yacht. But 25 years later, here we are. On Thursday, as the country recovered from state of emergency temperatures and amid an escalating cost of living disaster, Liz Truss sought to strengthen her case to be Britain’s next prime minister by pledging support for another national big ship.

“I do support the idea of promoting our trade around the world,” she told reporters in Peterborough. However – new broom and all that – she wouldn’t do it Boris Johnson’s way. Rather than expecting taxpayers to stump up the projected £200m cost, “what I would be seeking is to get investment into a yacht, looking to the private sector to assist with that to make it financially viable”. Sponsors with nine-figure marketing budgets, do step this way.

What is it about the thought of a big British ship that gets some people so excited? The Daily Telegraph has been campaigning for one since 2016, not coincidentally the same year the paper and its then columnist helped secure Brexit. Johnson announced last May that a new “national flagship” would indeed be built, “reflecting the UK’s burgeoning status as a great, independent maritime trading nation”.

The Ministry of Defence, with a £16bn backlog in its equipment budget, isn’t keen to pick up the tab, however. Truss’s rival Rishi Sunak, while chancellor, was also at odds with Johnson on the subject, with a source telling the Sunday Times last year that there was “a huge row” over funding; another described the yacht plans as “a complete and utter shitshow”.

The British royal family has had its own yacht since 1660 when Charles II, newly restored to the English throne, bought the small coal ship on which he had fled for France a decade earlier, naming it, rakishly, HMY Royal Escape. Eighty-two ships later, Britannia was launched in 1953 with a bottle of “Empire wine” – a rationing-friendly substitute for champagne.

The new Queen and her husband were closely involved in its design, which made it “rather special”, the Duke told an interviewer in 1995: “All the other places we live in had been built by predecessors.” Britannia was extensively used by the royal family and in almost 1,000 state visits, but became increasingly costly to maintain and Tony Blair took the decision in 1997 not to recommission it, a decision (unlike some others) that he later said he regretted.

Today, however, it is not clear who really wants a yacht. Not the public – YouGov found only 29% in favour last year. Not the royal family, who were unhappy about plans to name a new ship after the Duke of Edinburgh and have called it “not something we have asked for”.

Senior military figures aren’t keen either, among them R Adm Chris Parry, a former senior naval commander (“Frankly the narrative around this has been really poor. And the designs I’ve seen – I wouldn’t go to sea in that”). And many Tories, too, agree with Lord (Ken) Clarke who told the BBC it was “silly populist nonsense”.

Six weeks before Conservative members choose Britain a prime minister, however, Truss knows that talking about a yacht while saying she wants to privately fund it “allows her to pledge support for the idea without it ever happening,” as Sunder Katwala, director of the thinktank British Future, noted.

Sunak, meanwhile, is yet to be drawn on his plans for the yacht if he wins, though as some have observed, if need be the multimillionaire could comfortably fund it himself.