Fresh Prince of Bel Air blows into Brixton (and MP Chuka Umanna plays Will Smith's dorky cousin Carlton)

Will Smith at a school in Brixton

Complete the following sentence. “In West Philadelphia born and raised…”

If you just said “… on the playground is where I spent most of my days”, congratulations. You were young in the 90s. If these words mean nothing to you, take a minute, just sit right there, and I’ll tell you all about the Fresh Prince of Bel Air.

On Thursday, Will Smith surprised pupils at a school in south London by heading a special assembly. At the end of the event, set up by local Labour MP Chuka Umunna, he performed a song that he wrote with legendary producer Quincy Jones more than two decades ago.

Remarkably, nearly every pupil at St Martins-in-the-Fields High School for Girls, as well as several members of staff, could sing along word for word.

The song was the theme tune to the Fresh Prince of Bel Air – a 90s sitcom that has had an extraordinarily long afterlife since its last episode aired way back in 1996.

And while Will Smith has since become one of Hollywood’s most bankable stars and sold millions of records, the theme tune still follows him wherever he goes.

“It’s taken on a life its own,” said Dan Stubbs, news editor and “in-house Will Smith expert” at NME Magazine. “For a certain generation, Fresh Prince was 6 o’clock, after school, tea-time viewing and the theme tune is insanely catchy. It’s not surprising as he was a proper hip-hop artist and the producer, Quincy Jones, knows a few things about making a catchy tune. It wasn’t a Denis Waterman situation.”

The song, as anyone under the age of 35 will attest, sets up the premise of the sitcom, explaining how a fictional version of Will Smith, a street-wise Philadelphia boy, is sent to live with his wealthy aunt and uncle in Bel Air, California, after getting into a fight.

The show remains popular, is still regularly shown on Viva and MTV and appears to have developed cult status.

Even Mr Umunna counts himself a fan. “I used to watch the Fresh Prince of Bel Air when I got back from school. We all grew up with Will Smith,” he told The Independent. “The funny thing was seeing all the school girls, now the age that I was in the 90s, all knowing the words as well.”

It comes as no surprise perhaps that Mr Umunna, at 34, should know his Uncle Phils from his Jazzy Jeffs. He also recalls buying Will Smith’s 1991 album Homebase, which featured the hit song “Summertime”.

But does he know the words to the theme tune? Put to the test, Mr Umunna could not recite the next line to a lyric from the song, and there have been some who have described his dancing during Will Smith’s school performance as reminiscent of a certain Carlton Banks – Will’s dorky but endearing cousin in the show. He confessed that for a politician, dancing was always a “risky thing”.

Smith was in London this week to accompany his 14-year-old son Jaden – a rapper and actor like his dad who is supporting Justin Bieber in the latter’s ill-fated London tour appearances.

Mr Umunna contacted Smith offering to show the rapper “the real London” and the pair, joined by Tessa Jowell, toured Brixton on Thursday, culminating in the surprise appearance at the school for girls aged 11 to 18.

His appearance was kept a closely guarded secret until the very last minute.

“When I was asked, at very short notice, if I was prepared to host a visit I was going to say no until I found out it was Will Smith” said head teacher Lesley Morrison. “I was expecting someone like Michael Gove and I really wasn’t in the mood for him at all.”

“Will is such a legend, a hero for all the films that he’s done and being the first rapper not to use profanities,” she said, adding that she was pleased that her pupils, none of whom were born when the show began, were aware of the Fresh Prince of Bel Air.

“The show is still hilarious, a bit like the Cosby Show – funny to a point but positive. There’s so many awful things that they could be watching, but the fact they know the song shows that not all kids just want to watch shows with violence and sex these days.”