'Now, what I want is, Facts." So says the schoolmaster Thomas Gradgrind in the opening sentence of Charles Dickens's Hard Times, a novel in which the great author satirises those who mistake information for learning, and repetition for knowledge.
Yet to be considered a true Brit these days, facts are exactly what you need. Ever since the Conservative politician Norman Tebbit's infamous observation in 1990 - that immigrants who root for their native team in sporting events rather than Great Britain may not be sufficiently loyal - government has attempted various methods to gauge whether those applying for British naturalisation truly intend to integrate into the culture. Or are simply economic migrants flying under a flag of convenience.
The latest manifestation is the "Life In The United Kingdom" citizenship test, an examination consisting of 24 questions covering topics such as British society, government, everyday life and employment. Any aspiring immigrant must take the test as part of an overall assessment of an application.
The trouble is, of course, what constitutes being British? You may think a predilection for fish and chips, and a love of football would be sufficient national credentials, but nowadays the most popular meal in the UK is curry, while the majority of Premier League clubs are foreign owned.
When the British runner Mo Farah won his two gold medals at the London Olympics, his triumph was celebrated the length and breadth of the country. Here was a Somali immigrant who moved to the UK when he was 8, armed with barely a word of English: exactly the sort of individual who would have struggled with this new test.
But he's not the only one. Earlier this week I took the official citizenship "practice" exam to test my own national credentials. The exam is available online to provide a dummy run for those considering the real thing. I approached the ordeal with some confidence, yet it was a chastening experience. Of the 24 questions, I answered only 12 correctly, and thus it was no surprise to find out that I had ignominiously failed. Given that I've lived in Britain for all of my 55 years, the result suggests that either the exam - or I - have a lot to learn about the national culture.
Even Prime Minister David Cameron has found out just how intangible a quality "Britishness" is. On Thursday, he appeared on the David Letterman programme in the United States, an appearance that he may now regret.
The primetime show, broadcast nightly on CBS and watched by millions, was presumably intended to give Mr Cameron an opportunity to pontificate on world events and to raise his transatlantic profile. Letterman, however, had other ideas.
"Do you mind if I ask you a lot of dumb American questions?" Letterman asked, before launching into a series of posers on British history and culture that mirrored the sort of questions an aspiring immigrant might expect on the official test. While Mr Cameron started confidently enough, he soon foundered.
Not only was he unable to answer a question about the identity of the composer of Rule Britannia (Mr Cameron answered Edward Elgar; in fact, it is Thomas Arne), but when the questions turned to the Magna Carta - the most important social document in British history - things got even worse.
Although Mr Cameron correctly identified where it was signed - Runnymede - he was unable to provide a translation from the Latin, which is "great charter".
Letterman, of course, watched gleefully at his guest's obvious discomfort like some malevolent schoolmaster. Mr Cameron, meanwhile, did his best to take it all in good stride, bearing his embarrassment stoically and managing - just - not to look too furious at this cultural ambush.
As Mr Cameron flew home to the country of his birth, he'll no doubt be spending his time studying Winston Churchill's four-volume A History of the English-Speaking Peoples rather than government documents and opinion polls. And at his arrival at Heathrow, he will, I imagine, be hoping UK customs officials don't ask him to complete a citizenship test before allowing him to re-enter the country. Otherwise, he may find he has a longer spell abroad than he had anticipated.
Michael Simkins is an actor and writer based in London
On Twitter: @michael_simkins