Dizzee Rascal opened with his trademark self-introduction “Jus’ a Rascal”, an apologia pro vita sua rapped in a careering East End accent. Yet this was not the usual Rascal.

For a start, he was trying not to swear, with mixed success. Then there was the presence of a string orchestra, horn section and rock band. Seasoned Dizzee watchers looked around for DJ Semtex, the rapper’s usual man behind the decks, but of Semtex there was no sign.

The occasion was the Electric Proms, the BBC’s pop version of the Proms. Other acts appearing in the mini-season, which ends Saturday, include Robbie Williams, Dame Shirley Bassey and Smokey Robinson – unusual company for an east London rapper from the wrong side of the tracks who partly composed his first album on his mobile phone.

That album, Boy in da Corner, won the Mercury prize in 2003. Since then Dizzee, real name Dylan Mills, has become the UK’s most successful rapper, scoring a hat-trick of number-one singles in the past year.

His move from “grime”, the gritty rap subgenre he spearheaded, to crossover hits had provoked purists to carp about selling out. But Dizzee’s musical curiosity was there from the beginning. As he rapped on his last-but-one album: “I’m in the world now, I gotta explore it:”

This was his first live show with backing musicians. Thrash guitar and drums turned “Jus’ a Rascal” and “Road Rage” into sludgy 1990s rap-metal – a questionable homage to the likes of Rage Against the Machine, though Dizzee’s nimble flow gave it punch.

The transformation of “Can’t Tek No More” from reggae-sampling lament about social deprivation into jolly ska knees-up was fun but not entirely appropriate, while sonorous string arrangements gave dubious gravitas to the stark inner-city sexual politics of “Jezebel”.

Yet the experiment paid off more often than not. “Stand Up Tall” was awesomely mashed up with Nirvana’s “Smells Like Teen Spirit”, “Pussyole (Old Skool)”, censored as “Old Skool”, was given a superb old-school rap makeover, complete with Mark Ronson-style horn break, and “Holiday” featured inventive flamenco guitar. “Imagine if I showed you one day I was leaving the ’hood,” he rapped towards the end. He has done so in style.