SIGMA - for those who don't know - is the 18th letter of the Greek alphabet and the symbol for a complex mathematical equation.

Oh, and it's also the name of a platinum record-selling drum 'n' bass outfit who, as far as making chart-storming music is concerned, certainly know the right formula.

Last Friday, Sigma – who are Harpenden's Joe Lenzie and Cameron Edwards from Manchester – had the highest-ranking new entry in the UK Top 40 Singles Chart, blazing in at number four with Glitterball, featuring vocals from X Factor finalist Ella Henderson.

And it’s just a taste of the success the friends have been enjoying this summer as they work their way through an exhaustive array of festivals including Radio 1’s Big Weekend, Glastonbury and V Festival later this month.

"The summer has probably been the busiest of our lives I guess," says former Sir John Lawes School student Joe.

"We have done loads of festivals and loads club shows and we have been out in Europe quite a lot.

"We have got a residency out in Ibiza at Amnesia and Ibiza Rocks and we have got a residency in Mallorca at BCM – it’s been really fun. We have played some really cool shows."

It's not bad for a band who were relatively unknown in the mainstream pop charts until last April when their single Nobody to Love - a reworking of Kanye West's Bound 2 - shot to No 1 upon its release.

Following their early success, the duo scooped another No 1 in September 2014 with Changing, featuring Paloma Faith, and went on to chart at No 12 in March 2015 with Higher featuring Labrinth.

Earlier this year they took their first live tour on the road in April, opened the 2015 TV BAFTAS and were nominated for a BRIT Award.

But their whirlwind year doesn't stop there as Joe and Cameron are off on another tour in October, ahead of the release of their debut album Higher in November.

"It’s just heads down, working hard and enjoying it," laughs Joe, who has recently returned from a well-earned break in Montenegro.

Regardless of their rising fame, Sigma still work from a make-shift studio in Joe's parents' shed in Harpenden.

Growing up in the picturesque town, Joe kickstarted his life-long obsession with music as a teenager when he took to the decks at venues such as the former Buzz Bar in Harpenden, The George and The Horn and joined St Albans group the Drunken All Stars.

Then in 2002 he won the prestigious DMC DJ finals at Brixton Academy as part of the team Flaredycats, reluctantly revealing that back then he was known as DJ Wooz.

Leaving home to study music technology at Leeds University, Joe met Cameron and the pair hit it off developing an addiction for mixing drum and bass music, raving and studying.

After university they began building their reputation as drum 'n' bass producers, regularly playing gigs in Europe and further afield.

But despite their wealth of experience performing live, Joe admits their relatively newfound super stardom still unnerves him occasionally.

One such moment came this summer, ahead of their slot joining Paloma Faith on the Pyramid Stage at Glastonbury.

"I think that’s one of the most nervous times I've had walking out on stage," remembers the 32-year-old.

He continues: "When we were stood backstage it was all quite jittery but it was a lot of fun when we made it out on stage.

"It was a bit of a moment. Especially when you see that many people - there’s like 100,000 people at the main stage - and they’re all going crazy which is great.

"It’s really good to see, especially because it’s drum 'n' bass music which is not usually the most well-received styles of music. It’s great to see it crossing over to that mainstream audience."

Sigma will play V Festival, Hylands Park, Chelmsford, on Sunday, August 23. Details: vfestival.com, sigmahq.com