Persistence and an obvious natural talent are behind the Camden resident’s fascinating ascension from IT worker to star of BBC Proms.

It’s a rare thing these days for a new orchestral score to bear the title ‘symphony’: there’s too much baggage carried by that word, too many daunting expectations. But the other week brought a spectacular new symphony to the BBC Proms by the newly knighted Sir James MacMillan, his 4th. And next Tuesday sees the premiere of another – with no designated number but I guess you could call it No.1 – by the fascinating Hong Kong-born, Camden-resident composer Raymond Yiu.

Chinese composers active in the UK are conspicuous by their rarity: you notice them. And Yiu got noticed with a vengeance back in 2006 when he produced a small-scale opera for the Aldeburgh Festival. Called The Original Chinese Conjuror, it was based on the true story of an American stage magician who passed himself off as Chinese (it was part of his act), got famous, but then died when a bullet-catching trick misfied. Quite literally.

Yiu’s robustly entertaining piece played in a theatre on the end of Southwold Pier, then came to the Almeida here in London, and has since been to Vienna. And en route its spunky, roller-coaster ride through alternating sound-worlds – East/West, Broadway/Operatic – in a seamless, breathless flow turned heads. Which made it all the more remarkable that when he wrote it, Yiu was only a part-time-composer. With a day job, working in IT.

As he recalls, “the commission came through rather late, so I had to work round the clock to fit the writing in with what I was actually employed to do. I think I slept three hours a day for ten months to get it finished in time, and by the end I was so burnt out I wrote nothing else for the next two years.”

That the commission came at all was in itself remarkable for someone with his background. He arrived in the UK in 1990, aged just 17 and on his own, sent over by his parents for two years of sixth-form education at a boarding school in Canterbury. His interest was science, and he went on to study engineering at Imperial College, shifting to computers before graduation.

But by then, he’d started to compose, entirely self-taught from hard listening, an aptitude for reading scores, and boldly unsolicited approaches for advice to major figures in the music world, like the American composer Lukas Foss.

Persistence and an obvious, natural talent paid off in 2002 with a radio performance by the BBC Singers and a take-up by the London Sinfonietta. But it wasn’t until after the success of Chinese Conjuror that he felt able, in 2009, to leave IT and dedicate himself to music.

Not unnaturally, he wanted to explore the way his Chinese cultural heritage could make connection with the modern English music world – which as it happened was of interest to him even as a child in Hong Kong. After a brief dalliance with Cantopop – the hard, commercial hits that are the necessary soundtrack to a street-cred Chinese youth – he found himself bizarrely drawn to Elgar, William Walton and Vaughan Williams: music he still loves, alongside Janacek, whose quirky unpredictability he has absorbed into his own work.

Recent scores include a chamber piece commemorating the 20th anniversary of the Tiananmen Square protests (for which he won a coveted BASCA award) and, summing up his East/West explorations, a quintet for piano and traditional Chinese instruments that premiered at LSO St Luke’s with no less a figure than Lang Lang at the keyboard.

His new Symphony, he says, has no specific Chinese content; but it is a work that references his past – and, in a broader sense, the past of everyone who hears it.

“It’s all based on memory’, he explains, ‘which if you think about it is fundamental to the way the traditional structure of symphonic music works. You present material, you come back to it, you look at it differently”.

That said, Yiu’s new piece doesn’t stay within tradition. There are, as he calls them, five-and-a-half movements (the half being a short intermezzo between movements four and five), and there’s the unusual addition of a solo role for countertenor, who sings words from memory-related poems.

Cavafy, Walt Whitman and John Donne all feature. But the central focus is a poem about AIDS by Thom Gunn, In the Time of Plague.

Yiu says he’s given it a 1980s disco setting, which should cause the audience to sit up. And specific memories of living through the AIDS crisis have clearly been a driving force behind the symphony as a whole.

“When I first came to London”, he says, “AIDS seemed to encircle my life. People just vanished, everyone was afraid. And it’s something that stays with me in my mind. You don’t forget something like that”.

A Proms commission performed by the BBC Symphony Orchestra under conductor Edward Gardner, Raymond Yiu’s Symphony premieres at the Royal Albert Hall on Tuesday August 25 alongside works by Britten, Janacek and Nielsen. It’s a 7.30pm start, with live broadcast on BBCRadio 3.