Aspiring Shropshire singer joined on stage by Ellie Goulding

Martha Edwards, 20, from Hopton, near Shrewsbury, thought she was recording a cover of the pop star's new track Army with her best friend when the Starry Eyed singer surprised them and joined the pair on stage.

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The Brit Award-winning singer-songwriter, raised in Herefordshire, took part in the secret as part of MasterCard's Priceless Surprises campaign, which is running alongside this year's awards.

Miss Edwards, who goes to King's College in London, was singing with Lucy Taylor for what she thought was a documentary about music superfans. But during the recording, a curtain lifted on the recording booth to reveal they were on stage performing in front of an audience.

Then Ellie Goulding herself stepped out on stage to perform the track alongside them. Miss Edwards said: "It was the best moment of our lives. I can't believe it really happened. There was a time when I thought I would never be able to sing again because of medical problems, and I've just sung on stage with Ellie."

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Last year, Miss Edwards secured a deal with PopShack, the world's first entertainment network for YouTube music stars.

She is in her second year studying a comparative literature degree and previously studied at Shrewsbury High School and Shrewsbury Sixth Form College.

She had dreamed of being a swimmer but at the age of 11 was diagnosed with scoliosis and had to have two operations to correct the shape of her spine. She was then diagnosed with pectus excavatum, a deformity of the chest wall which occurs in about four in every 1,000 people.

Ellie said: "It was amazing to surprise Martha and Lucy. They are so talented and nailed some tricky harmonies. Army is about my best friend so it was great to surprise two best friends. Their reaction was so worth it."