How old is 'Big Ben'? The trivia Meghan Markle must know to become British

Before US actress Meghan Markle becomes a British citizen after marrying Queen Elizabeth's grandson Prince Harry, she'll have to learn who opened Britain's first Indian restaurant, the size of the Lake District and the age of "Big Ben".

The details are potential questions would-be Britons face when they take a "Life in the UK" test, which all applicants must pass before becoming British citizens, answering a minimum of 18 out of 24 questions correctly.

Despite marrying into the royal family on May 19, Markle, 36, will herself have to successfully navigate the test and demonstrate sufficient knowledge of historical facts and some obscure British trivia, such as the height of the London Eye ferris wheel.

However, many of the questions - of which there almost 3,000 - are alien to those born and raised in Britain.

"How difficult are them questions?! They're too difficult," said 46-year-old chef Tony Poston, who was shell-shocked after he failed a practice test with a result of 58 percent.

"I did history at school but some of them are just absolutely stupid," he said, with his mouth wide open in astonishment.

Another Briton, Jenny Tate, a 53-year-old practice manager from London, was almost hysterical after she failed the test.

"I'm so sorry about that. That's shocking. That's actually quite hard," she said.

Not all the questions require an acute knowledge of history dating back centuries or knowing the height and age of well-known landmarks.

There are some questions about modern-day British life - you need to know that a general election is held every five years, and that it's illegal for anyone under the age of 18 to buy tobacco, amongst others.

But the test has come under fire by politicians and academic critics who say it serves no purpose, and that the majority of questions are absurd.

"It's gone from being something about practical trivia, to the purely trivial," said Professor Thom Brooks, 44-year-old Dean of Law at Durham University.

Brooks, originally from New England in the United States, is personally familiar with the test, having sat the quiz in 2009 ahead of becoming a UK citizen two years later.

He said it was irrelevant to British everyday life and the government had changed it in 2013 to remove useful information such as registering with a doctor and how to report a crime. One applicant, he said, had failed it more than 60 times.

Last month, a report by Britain's House of Lords committee on citizenship agreed with Brooks and said the government should carry out a comprehensive review.

"You've got stuff in the handbook anyway, about how tall is the London Eye? How big is the Lake District? And who set up the first curry house, what was it called, and what street was it on? Do facts like this, are these required to becoming British, or to integrating?" Brooks asked.

"It's a British citizenship test that very few British citizens can pass."

The London Eye is 443 feet (135 metres) tall, the Lake District covers 885 square miles (2,292 kilometres), Big Ben's clock is over 150 years old, and Sake Dean Mahomed set up the first Indian restaurant in London in 1810. The Hindoostane Coffee House no longer exists, but a plaque commemorating Mahomed - who died in 1851 - is there in its place.

A random survey carried out by Reuters found that out of 41 Britons, only 23 could answer questions they were shown correctly.

The 50-pound ($69) citizenship test is one of the hurdles Markle faces as she gives up her US nationality to become British.

The complicated process, which Britain has made harder in recent years in an attempt to cut net immigration rates to less than 100,000 a year, requires Markle to have lived in Britain for three years, to have good knowledge of English and to be of sound mind.

The requirement of earning a combined income of at least 18,600 pounds should not prove to be too burdensome for a prince of the realm and his new wife, however.

For many applicants though, the citizenship test is a major stumbling block. The most recent official figures showed that 133,490 tests were taken in 2016 with 47,312 failures.

Despite her new royal status, Markle will not be exempt for learning how many lawmakers sit in the Scottish Parliament or when Mahomed, who opened Britain's first curry house, was born.

"She really will have to do the test so it won't be any wave of the hand of her majesty that will change it," Brooks said.

Alanna Varshney moved to London from California in 2009. She passed the citizenship test in February of this year after vigorous preparation - online practice exams, studying the guidebook, making flashcards and quizzing her British husband.

She thinks most Brits would be "stumped" by the facts and figures that she had to learn, but got lucky with one particular question during her exam.

"My favourite was about which colony in 1776 declared its independence from the United Kingdom," said the 38-year-old who works in marketing, recalling the moment she burst into laughter and got a funny look from the adjucator during the exam.

"If I hadn't got that one right I would have felt really ashamed."

Although Varshney succeeded, some of the Britons quizzed by Reuters thought Markle might fare better than they had.

"She's a bright girl, she might get half!" grinned retired engineer David Armstrong, 58, after himself failing multiple answers.