Mitt Romney is to meet British Prime Minister David Cameron in London on Wednesday, during a fundraising and Olympic visit by the Presidential hopeful.

The meeting, which will take place at the PM's official residence of number 10 Downing Street, is fraught with potential political faux pas. After all, the sitting PM is not -- according to a Downing Street spokesman who confided to the Telegraph --  supposed to meet candidates in elections in foreign countries.

What's more, Romney will even walk through the famous black front door, and not slip in round the back like a then Senator Obama did when meeting Gordon Brown in 2008.

Cameron will, however, not meet him at the threshold, as he usually does with visiting heads of state, but greet him inside Number 10 instead.

Romney and Cameron have not exactly had the best of build ups to their first meeting either. When the PM visited the U.S. earlier this year he famously joined the President aboard Air Force One on a trip to the key swing state of Ohio, later attending a gala White House fundraising dinner. He also failed to meet Romney at all during his whistle stop love-in with Obama.

But, door etiquette and Air Force One bragging rights aside, as the pair prepare to finally shake hands on Wednesday it is their different experiences of Britain's National Health Service (socialized heath care to every right-thinking  Romney-ite) that could really set the cat among the pigeons.

According to the Telegraph: In 1995, his [Romney's] third son Josh was a young Mormon missionary posted to northern England. Navigating the A1 in a small Volkswagen, he knocked on doors from Mansfield to Ripon, spreading the word of Jesus Christ of Latter-Day Saints to working-class Britons unaware that he was the scion of Massachusetts millionaires.

One day in Sheffield, however, a stomach complaint led him to a local doctor, who had terrible news: symptoms indicated that he might have colon cancer.

Recalling the event, Romney later added: The waiting time for a colonoscopy was six weeks - enough time to make an operable, curable cancer become an inoperable terminal condition.

This just wouldn't do, so the Bain Millionaire, naturally, paid for his son to visit a private clinic instead. The cancer turned out to be a false alarm.

Cameron, a fellow conservative leader, has exactly the opposite experience of the NHS. His son Ivan, born in 2002 with severe epilepsy and cerebral palsy, was constantly in and out of NHS hospitals before his tragic death in 2009.

I have a child who's not too well, so I've seen a lot of the NHS from the inside, Cameron said in 2006, several years before becoming PM.  

In fact, he added,  in the last three years, I've probably spent more time in NHS hospitals than any politician apart from the few doctors in the House of Commons. I've spent the night in A&E departments and slept at my child's bedside. I've got to know the people who dedicate their lives to helping others. I've met so many miracle workers who are the real jewels in the NHS crown.

I want us to leave no one in any doubt about how we feel about the NHS today. We believe in it. We want to improve it. We want to improve it for everyone.

Despite their mutually privileged upbringings, and their right-wing bent, Romney has at least one fundamental difference in common with Cameron that could make for a reception far frostier than even the coldest of British summers can conjure.