Remember that glorious photo from Barbara Bush’s funeral of four of the US’s past presidents and their spouses … and Melania Trump, without her husband, the current inhabitant of the White House?

We were told Donald Trump skipped Mrs Bush’s funeral to avoid creating a security disruption. Nothing out of the ordinary, apparently – USA Today said it was traditional for first ladies to represent the president at the funerals of other former presidents’ wives.

Instead, Mr Trump went to his Mar-A-Lago estate in Florida, tweeting: “Heading to the Southern White House to watch the Funeral Service of Barbara Bush. first lady Melania has arrived in Houston to pay our respects. Will be a beautiful day!”

But now reports have emerged that Mr Trump has been specifically told not to attend the planned memorial service for Senator John McCain. The 81-year-old senator has brain cancer and an uncertain prognosis.

According to The New York Times, the White House has been told that Vice President Mike Pence will be welcome at Senator McCain’s planned memorial service at Washington’s National Cathedral, just a few kilometres from the US President’s official residence. Mr Trump will not.

By contrast, Barack Obama and George W Bush are expected to give eulogies at the service.

McCain only wants real Presidents at his funeral not ones that got captured by Russians

— Y (@radiochick841) May 8, 2018

Senator McCain and Mr Trump are both Republicans but have long had a rocky relationship. In 2016, while running for office, Mr Trump said Senator McCain, considered one of the US’s best-known Vietnam prisoners of war, was regarded as a hero only “because he was captured”.

“I like people who weren’t captured,” Mr Trump said.

They have also locked horns over Obamacare. Senator McCain was a supporter of Barack Obama’s signature healthcare policy, while Mr Trump was staunchly opposed to it, and fought hard to repeal it.

“Democrats are laughingly saying that McCain had a ‘moment of courage’,” Mr Trump tweeted during debate about the law.

“Tell that to the people of Arizona who were deceived. 116 per cent increase!”

Senator McCain’s reported request for Mr Trump to stay away has sparked a row among Republicans. Utah senator Orrin Hatch apologised to Senator McCain after initially calling the plan “ridiculous”.

Senator Hatch said Mr Trump was not only President, he was also “a very good man”.

“He would be a very interesting speaker and would do a good job for John,” he said.

He withdrew his comments after Senator McCain’s daughter, Meghan, called for calm.

.@MeghanMcCain tells us her father is having a "great recovery" and is "making jokes": "I'd like everybody to take a collective breath and chill out on my dad for a second…" https://t.co/Vhegu0pXqb pic.twitter.com/duPSM9GRJq

— The View (@TheView) May 9, 2018