Janine O'Malley, 44, an Australian national, passed the $70 test in 2016 but has now moved back to Sydney with her English husband and young daughter.
Giving Markle a taste of what she can expect, O'Malley said she found the exam intimidating and the invigilators overly strict.
"I had a bad cold and wanted to take in my tissues, water and cough sweets and snuck them up the sleeve of my top, but I was patted us down before going into the exam room and my 'contraband' was taken away," she said.
"They made us push up our sleeves to our elbows to make sure no one had used their arms as a cheat sheet."
» How to watch and stream the Royal Wedding (plus everything else on TV about Prince Harry and Meghan Markle)
British-foreign couples "need to show the genuineness of their relationship, that the (partner) meets the English language requirement" and that the Briton has a $25,000 minimum annual income or cash savings of at least $84,000 for the six months before the application for a spouse, said Lucy Garrett, an immigration lawyer at London-based firm Magrath Sheldrick.
The minimum income requirement isn't an issue for 33-year-old Harry — his net worth is at least $25 million.
The applicants must also prove they "can accommodate themselves adequately" by providing information like how many rooms are in their home, Garrett added. The newlyweds will live at Nottingham Cottage on the grounds of Kensington Palace after their marriage. The cute property has two bedrooms, two reception rooms, a kitchen and a bathroom, according to British media reports.
The application for British citizenship costs about $1,800.
Markle has already been granted "leave to remain" in the U.K. as the partner of a British citizen, a Kensington Palace spokesperson said.
» Meghan Markle confirms dad will not attend royal wedding
The palace said Markle "went through the normal processes" herself to get her visa.
A '"leave to remain" visa means Markle can stay in the U.K. subject to certain conditions (such as being granted working and welfare rights). The palace did not specify whether any conditions were attached to Markle's visa.
Garrett thinks Markle may be on a fiancée visa, which requires the holder to marry within six months. That would "also explain the quick turnaround" of the wedding, she said. The pair announced their engagement in November. Reports that they were dating surfaced in October 2016.
Markle must spend five years in the U.K. after her marriage to Harry before she can apply for "indefinite leave to remain," a visa category that has no restrictions. When she is approved for that, she can then apply for citizenship, Garrett said.
The requirements for spouses becoming British citizens include, according to the interior ministry, or Home Office:
- You're of sound mind, you're able to think and make decisions for yourself
- You're of good character, for example you don't have a serious or recent criminal record
- You've met the knowledge of English and life in the U.K. requirements
New British citizens have to attend a citizenship ceremony where they must swear an oath of allegiance to Queen Elizabeth II — Harry's grandmother — and pledge their loyalty to the U.K.
Immigration is a fraught topic in Britain at the moment, and the high number of migrants was one of the reasons its citizens voted to leave the European Union in 2016.
The U.K. government recently was harshly criticized for its treatment of the children of the Windrush generation — immigrants from Britain's colonies in the Caribbean whom authorities in London enlisted to help rebuild the U.K. in the aftermath of World War II.
Many individuals fell afoul of the government's "hostile environment" policy aimed at reducing net immigration. A number lost their jobs and were deported because they did not have the correct documentation to prove their rights to live and work in the U.K.
Others who left the country found themselves prevented from returning.
Markle could decide to become a dual citizen, but that would also mean potential dual taxation on her income — by America and Great Britain. It's a major reason why American "tax exiles" often formally renounce their American citizenship and choose to move somewhere else, say the Caribbean, according to Harry Drozdowski, a tax and estate attorney at Pasadena-based Anglin Flewelling Rasmussen Campbell & Trytten.
Markle, of course, would not be the first American to take on a new citizenship and keep her American citizenship — but she would be the first to be welcomed into the royal family.
Renouncing U.S. citizenship is not advisable for ordinary Americans, Drozdowski said, because they lose their right to vote, their right to representation by American diplomats if they get in trouble abroad, and their right to hassle-free return to the U.S. for visits without getting a visa.
But none of that is likely to be a problem for Markle if she becomes a full Brit: As a royal, she can't get involved in politics anyway, including voting. And she can be sure the British government will do everything it can to protect her no matter where she is.
And blocking an American-born princess from visiting her mother in Los Angeles? Doubtful, Drozdowski scoffed.