Rishi Sunak has dug himself into a hole entirely of his own making. I fear he's lost it, says Nigel Nelson

Wherever you look, they are behaving so irrationally I’m beginning to wonder whether extraterrestrials have popped in for a visit to replace their brains with cosmic dust programmed to deliver nonsense.

Rishi Sunak’s brain is of particular concern because it seems to have turned to mush. It’s the only explanation for his odd behaviour over the last few days.

At PMQs Keir Starmer called it a “one man war on reality” and accused Mr Sunak of being “lost in la-la land.”

The bizarre row over the marbles - or Parthenon sculptures as the Greeks more respectfully call them - gave the Opposition leader a good opening gag about an ancient relic most British people have lost interest in. “But that’s enough about the Tory Party,” Sir Keir added.

Mr Sunak has dug himself into a hole entirely of his own making. Greece has a long-standing policy of wanting the marbles returned to the Acropolis Museum in Athens because they are part of their heritage not ours. A trip to the Acropolis last month reinforced my view that is right.

Imagine the outrage here if the boot was on the other foot and Greece was hanging on to a few pillars from Stonehenge.

But the UK has an equally long-standing policy to keep the priceless Greek goodies in the British Museum on the grounds we’ll look after them better.

It was never much of a justification, but collapsed when it was revealed a museum staffer had been filching stuff for years. Presumably the marbles were only safe because he couldn’t fit them into his briefcase.

The PM and his Greek opposite number Kyriakos Mitsotakis could have sat down over an Earl Grey cuppa in No10 and taken five minutes to agree to differ before moving onto more important matters such as migrant crossings, Russian double-crossings and Israelis being very cross.

Instead Mr Sunak threw his toys out of the pram - bat, ball and marbles - and told Mr Mitsotakis to go boil his head for daring to have a moan on telly, a diplomatic faux pas by Mr Sunak which ranks with Silvio Berlusconi complimenting Barack Obama on his tan.

The PM’s childish tantrum only served to open up an unnecessary debate, not just over the marbles, but the other ancient artefacts the British Empire acquired in questionable circumstances over the years; the Rosetta Stone we nicked from the French after they nicked it from the Egyptians; the koh-i-noor diamond the East India Company half-inched from a Punjabi boy king.

Even Queen Camilla chose to avoid wearing the bling at the Coronation because of the sensitivities surrounding its ownership.

This is not how things are meant to be done. Whenever our ministers go to a country with a less than exemplary human rights record there is an understanding they must mention it and move on swiftly.

Foreign Secretary David Cameron will tell the Saudis we don’t approve of them chopping their citizens’ heads off and the Saudis will tell us to mind our own business. Box ticked.

The chat then turns to what the talks were intended to be about such as buying extra oil and selling British jets to drop more bombs on Yemen.

This is not the only example of Mr Sunak losing the plot. He tied himself in knots at this week's Global Investment summit by lauding our “competitive visa regime” and boasting about overseas graduates being able to bring their families to Britain for two years.

Not the most diplomatic way to appease Tory MPs getting themselves in a paddy about a record 745,000 legal migrants.

And the PM is still toying with legislation declaring Rwanda a safe and enlightened country even though the facts say different - such as the Kigali regime sending over hit squads to take out Rwandan exiles living here.

Mr Sunak could pass a law saying he is 6 foot 2 and the Supreme Court would have to accept it. But it wouldn’t change the fact he’s 5 foot 7.

Immigration was the main theme at PMQs. But Tory suggestions for solving it really are something out of la-la land.

Capping the number of health and social care visas issued and increasing the salary threshold from the shortage occupation discount of £21,000 to £35,000 would certainly help stop nurses and care workers coming here.

It would also add to the 47,000 current vacancies in nursing and 152,000 unfilled posts in the care sector and increase the 7.8million now languishing on hospital waiting lists.

Immigration is not a numbers game which can be dealt with in isolation from everything else.

A bit like a game of marbles really. There’s a knock on effect when one bangs into another.