Currently one of the most successful artists in the world, Ed Sheeran has been accused of copyright infringement, in a suit that could make pop music history. The writers of ‘Amazing’, a song which was recorded by X-Factor winner Matt Cardle and released in 2012, have filed a $20 million action against Sheeran. They allege he plagiarised their work for his hit single ‘Photograph', released in 2014.

The songwriters – Martin Harrington and Thomas Leonard – have also written for Kylie Minogue and Emma Bunton, so they are no ingenues merely looking for notice. Nor is their lawyer: to represent them, they have hired Richard Busch, the solicitor who took a similar case on behalf of Marvin Gaye's family against Robin Thicke and Pharrell Williams, over the single 'Blurred Lines’ – and won.

The songwriting duo claim that Sheeran's single copies ‘Amazing’, which they co-wrote in 2009, "note-for-note".

As yet, Ed Sheeran has offered no response to the allegations.

There is a bizarre twist to the story, which in many ways contradicts the theory that the fundamental element in the success of any recording is the song! As the third single from Cardle’s debut album Letters, ‘Amazing’ climbed no higher than No. 84 in the UK chart. In contrast, ‘Photograph' sold more than 3.4 million copies worldwide.

The legal action was filed on behalf of Harington and Leonard on Wednesday, June 8, in a Los Angeles federal court.

The lawsuit goes into specifics about the nature of the alleged plagiarism. “The chorus sections of ‘Amazing' and the infringing ‘Photograph' share 39 identical notes,” it says, "meaning the notes are identical in pitch, rhythmic duration and placement in the measure."

And there is more.

"The song's similarities reach the very essence of the world,” the suit claims. "The similarities go beyond substantial, which is itself sufficient to establish copyright infringement, and are in fact striking. The similarity of words, vocal style, melody, and rhythm are clear indicators, among other things, that Photograph copies ‘Amazing'."

“It is a tricky one,” one music publishing industry insider told Hot Press. “I don’t think for a second that Ed Sheeran would have knowingly lifted sections from someone else’s song. There are similarities. But do they amount to enough to substantiate the accusations? That is debatable.

"The reality is that everyone in popular music is going to the same well for melodies, chord changes and even lyrics," he added. "Besides, music is so ubiquitous that there are times when it is scarcely possible to know whether or not you have heard a tune or been influenced by it. A lot of this stuff is subliminal. How the courts will view it is, of course, a different matter entirely."