LONDON: How tall is the London Eye? Who opened Britain’s first Indian restaurant? Who was the fifth wife of Henry VIII?

If Meghan Markle doesn’t already know the answers, she needs to start studying.

All three are potential questions on a test given to those who — like Prince Harry’s fiancee — want to become British citizens.

Kensington Palace says the California-born Markle intends to take UK citizenship after she marries Harry on May 19 at Windsor Castle.

But Markle will soon discover that it takes more than marrying a prince to become British. It also requires time, money, a good memory for obscure British trivia and the ability to untangle red tape.

Immigration lawyer Colin Yeo says the road to British citizenship is “insanely complex.”

“It’s very easy to make mistakes because the requirements are so very precise,” he said.

Britain’s royal family has become a lot more welcoming to American divorcees since the last time one tried to join the clan. When King Edward VIII wanted to marry twice-divorced Wallis Simpson, it sparked a constitutional crisis. The king abdicated in 1936, saying he could not reign “without the help and support of the woman I love.”

But while Britain is rolling out the welcome mat for Markle, it has placed ever-bigger hurdles in the way of less well-connected or well-funded immigrants.

Britain’s Conservative government tightened immigration rules in 2012 to help it meet a self-imposed target of reducing net immigration to less than 100,000 people a year. (It’s currently over 200,000). The target was set at a time when public attitudes to immigration were hardening. A desire to cut immigration was a major factor for many in the UK who voted in 2016 for Britain to leave the European Union.

But critics say the immigration rules are rigid and unfair, giving the affluent an advantage over the less well-off.

Non-EU citizens who marry Britons typically must obtain a spousal visa, then live in the UK for five years before they can apply for permanent-resident status or citizenship.

To get her visa, the 36-year-old Markle will have to provide evidence that her relationship with Harry is genuine and she really is divorced from her first husband, Trevor Engelson.

She also must show that Harry earns at least 18,600 pounds ($26,000) a year or has 62,500 pounds ($87,100) in savings, and can provide accommodation “without recourse to public funds.”

That shouldn’t be a problem for this particular couple — who can also afford the fees, which can amount to almost 7,000 pounds ($9,760) during the process.

But many less-affluent couples struggle to meet the cost. Between 2012 and 2014, 30,000 applications to bring a non-British spouse to the UK were refused. Yeo says the minimum-income rule has created thousands of “Skype families” in which parents are forced to live in different countries.

“(The rule) discriminates against women, young people and ethnic minorities, who are less likely to be earning more — and people outside London,” who on average learn lower wages, Yeo said.

Other prospective immigrants have been rejected because of increasingly stringent demands for documentation. The British government is currently facing intense criticism and charges of racism over its treatment of thousands of people who came to Britain from the Caribbean as children in the decades after World War II.

They had the right to live in Britain, but many have recently been denied jobs or medical treatment, or even threatened with deportation, because they cannot produce paperwork to prove their right to live here. The government has also admitted that in a clear-out a few years ago, it destroyed the landing records of many people from the Caribbean.

Caitlin Milazzo, a US-born academic who got British citizenship in January after living in the country for 6 1/2 years, advises Markle to pay attention to the details when she is preparing her application.

“The rules are quite complicated, but generally if you are up on the process it makes it a little bit easier to prepare,” Milazzo said.

Markle will doubtless have the best legal and administrative advice available and may also get special treatment. In exceptional circumstances, immigration officials are allowed to bend some of the rules.

But Milazzo hopes Markle won’t get an easy ride just because she is marrying a royal.

“They should just say there is one rule for everyone, rich or poor — these are the requirements that apply to everyone, no matter if you’re royalty or someone coming in as a nurse,” she said. “But I know that’s not how the world works.”

One thing Markle will find it hard to avoid is the “Life in the UK” test, a notoriously quirky set of questions covering everything from history and literature to customs and politics.

The test has been criticized for containing questions that few Britons can answer. The House of Lords Citizenship Committee said last week that the quiz appeared to be “a barrier to acquiring citizenship rather than a means of creating better citizens.”

But as a native English speaker, Markle will likely find the multiple-choice quiz easier than many applicants for whom English is a second language.

Law professor Thom Brooks, author of “Becoming British: UK Citizenship Examined,” advises Markle to learn the height of the London Eye Ferris wheel (443 feet or 135 meters), the name of the pioneering Indian restaurateur (Sake Dean Mahomed) and the identity of Henry VIII’s six wives to prepare for the test.

Brooks, the US-born dean of law at England’s Durham University, says the test is fairly easy to pass with the help of the official practice book, but brings the taker little practical benefits.

He likens it to “a bad pub quiz.”

“Pub quizzes are fun,” Brooks said. “This quiz wasn’t fun. And the trivia wasn’t even worth knowing.”