Stormzy has promised to deliver an ''iconic'' performance during this year's Glastonbury Festival.

The 25-year-old rap star will close the Pyramid stage on the Friday night of the festival, and he's assured fans they won't be disappointed by his performance.

He told BBC Radio 1Xtra: ''If you think I got booked for Glastonbury headline to come there and not give you an iconic headline performance, you've gone crazy.''

Some fans and critics have questioned whether Stormzy - who has only released one studio album to date - merits being one of the headlining acts at the festival.

But the chart-topping rapper has defended his credentials, saying he's a ''serious musician''.

He explained: ''There were so many doubters being like, 'Oh he hasn't got no number one song' or, 'Oh he's got one album out, he's not ready.' I'm there because I'm a serious musician.''

Earlier this month, meanwhile, Stormzy revealed he is currently working on a new album.

Asked about his future plans, he explained: ''The best way to describe my album is that I don't want no filler songs but I'm going to go an even further step and say I don't want a filler lyric.

''I don't want me to be saying anything that's wasted, anything that's just there because it rhymes. Literally every single thing is with purpose and with conviction and with expertise.''