The British rocker was due to play in a concert as part of a benefit show, The Ship We’re In, to raise money for The British Red Cross’ refugee awareness campaign at London's Royal Festival Hall on 19 June (16).

The gig was to close the Meltdown Festival, which this year (16) is curated by Elbow frontman Guy Garvey and runs from 10 to 19 June.

However the former Led Zeppelin singer is a defendant in a plagiarism case in Los Angeles regarding the band's 1971 hit Stairway To Heaven, which initially was scheduled to begin 10 May but has now been moved to 14 June (16). As a result, Plant has had to cancel his plans to perform in the special gig.

"It's with great disappointment that Robert Plant must cancel his appearance at this year's Meltdown Festival," representatives for the 67-year-old musician wrote on his Facebook page. "Robert is a defendant in a court case in LA which was due to take place May 10th. Through court rearrangements, the hearing has been moved to June 14th."

The copyright case against former Led Zeppelin members Plant and Jimmy Page, 72, was brought by Michael Skidmore, a trustee for the late Randy Wolfe, also known as Randy California, the lead guitarist of the band Spirit.

The lawsuit claims the band's classic hit Stairway To Heaven was plagiarised from Spirit's 1967 track Taurus, which Wolfe penned.

Last week (beg16May16) Skidmore's lawyer, Francis Alexander Malofiy, filed papers in a California federal courthouse asking a judge to compel the two musicians to appear in court for the trial.

Lawyers for Page and Plant indicated the pair would attend voluntarily and in a subsequent motion filed with the court, dismissed a claim by Malofiy that they were refusing to attend the Los Angeles trial.

In the Facebook post announcing he would be unable to attend the British Red Cross gig, Plant's representives wrote, "Robert has been enthusiastic to help in any way to the increased awareness and support of so many powerless and distraught peoples. Therefore the opportunity afforded at Guy Garvey's Meltdown was an event that Robert was passionately drawn to."

After Plant's cancellation, the charity gig, titled The Boat We're In, has subsequently been called off, with organisers blaming, "other factors" as well as the rocker's absence for the abandonment.