As the Albanese government pursues its AUKUS “optimal pathway” for acquiring nuclear-powered submarines, it’s experiencing another sub-optimal headache.

Two hours before Defence Minister Richard Marles was scheduled to have a personal tour of His Majesty’s Naval Base in Portsmouth on Thursday, his British counterpart John Healey dramatically resigned.

Secretary Healey’s sudden decision to quit over defence funding levels has caused shockwaves in Britain, putting further pressure on beleaguered Prime Minister Keir Starmer, and raising more doubts over the UK’s ability to deliver on the AUKUS deal.

The extraordinary political developments also revived memories of former Defence Industry Minister Christopher Pyne’s visit to the UK in 2017 where he declared online it was “great” to catch up with his host Michael Fallon, minutes after the Secretary had resigned.

Behind the scenes in Australia, some Labor MPs are privately joking that the UK’s current Defence Secretary had also chosen to resign, rather than endure yet another meeting with his Australian guest Richard Marles.

Greens Senator David Shoebridge, a leading AUKUS critic, could also hardly hide his glee at the overnight drama, highlighting another recent revelation that Australia will only receive second-hand submarines from the US, rather than one new boat and two already in-service.

“Defence Minister Marles seems committed to a process of ritual global humiliation as he does a world tour on AUKUS,” Senator Shoebridge told reporters on Friday.

“Maybe Richard Marles will say this was his plan all along – he didn’t want an ‘in-service UK Defence Minister’, maybe he will say that this is their new optional pathway with the UK”.

But for the government this development is no laughing matter, as it is yet again forced to defend progress on the massive $368 billion project to replace Australia’s ageing Collins-class fleet with nuclear boats.

Several hours after the Secretary’s resignation, Mr Marles issued a statement saying he deeply valued his relationship “with my good friend John Healey as Secretary of Defence, as I have with his predecessors on the Australia-UK defence relationship”.

“I have worked closely with all of them particularly in respect of AUKUS. Our defence relationship is enduring, with deep connections, values and shared interests,” he added before flying out of the UK.

Back home Defence Industry Minister Pat Conroy, who was last month left to explain the unexpected US decision to no longer supply Australia with one of its newer Virginia-class submarines, dismissed Senator David Shoebridge’s attacks as “juvenile”.

The overnight drama has highlighted growing concerns about the UK’s ability to deliver on the AUKUS project, amid warnings that the country’s military is now dangerously underfunded and ill equipped to meet rising strategic challenges.

It’s a warning also made here by Opposition Leader Angus Taylor who has again accused the Albanese government of not doing enough to fund the Australian military.

“Good on the Secretary of Defence in the UK for resigning and saying that defence spending needs to be higher,” Angus Taylor said on Friday.

“(Richard) Marles should be asking for defence spending to be higher in this country, because the truth is that AUKUS cannot be funded on the current budget”.

“It cannot be done other than by gutting the rest of the defence force, that’s the truth, and Marles our Defence Minister needs to get serious about getting the funding that is necessary to complete to deliver AUKUS”.

When resigning as Secretary, John Healey declared a target for spending 3 percent of GDP on defence in 2030 must be set but added: “I would not be able to accept a Defence Investment Plan settlement that does not give our forces the resources they need.”

In Australia the government is also vowing to get defence spending to 3 percent of GDP but several years later than its AUKUS partner.