They say it's the quiet ones who are the worst, but they might also be the best - at rapping anyway.

That's the conclusion we've come to after seeing Daniel Radcliffe showcase his unexpectedly good rap skills during an appearance on The Tonight Show Starring Jimmy Fallon.

The 25-year-old former Harry Potter child star was sporting a manly beard as he discussed his love for hip-hop with the chat show host.

Admitting that he enjoys trying to memorise and perform difficult raps, Radcliffe says he knows all of Blackalicious' Alphabet Aerobics.

"That's one of the trickiest, fastest songs I know," says an impressed Fallon - before raising a microphone into view and offering it to D-Rad.

As the star then takes to the mic, Fallon stands behind him and holds cards displaying each letter of the alphabet as Radcliffe works his way through the song - which gradually speeds up throughout.

His seemingly faultless rendition earns him a standing-O from the excited crowd, with Fallon hugging him and shaking his hand before quipping that he'll be "on iTunes this Friday".

At least we think it was a joke...