For the thousands of fans who had hoped to see the Zimbabwean musician Thomas Mapfumo, known as the "Bob Marley of southern Africa", in his headline slot at the Womad Festival last weekend, it was to be a disappointment.
It should have been a rare appearance by Zimbabwe's best-known and most politically engaged musician, but, despite his high-profile billing at the world music festival, Mapfumo was refused a UK visa.
And Mapfumo is not the only international musician who has been turned away from Britain this year because of visa regulations. A nine-strong Mozambique group, Djaaka, were deported from Gatwick airport last week on the way to an Italian festival because they lacked transit visas.
Four musicians from the Mauritanian singer Dimi Mint Abba's group will not be present when she performs at The Proms at the Royal Albert Hall this Friday, while an Edinburgh Fringe festival performer, Kieran Butler, has put a call out for a last-minute replacement violinist, after his partner, Michelle Wilson, was deported back to Australia. Immigration officials said she had worked in the UK without a permit.
It is feared that the summer's festival season could become blighted by visa regulations. So far, the refusals to grant visas to numerous highly respected musicians and artists has led to a spate of last-minute cancellations, and industry experts fear this could lead to a form of "cultural censorship" in future years, where acts presenting visa difficulties are avoided by festival organisers.
Home Office regulations state that someone can enter the UK as an entertainer without a work permit if "you hold a genuine invitation to perform at one or more specific events" but also that he or she must hold a valid UK entry clearance, presented to the immigration office on arrival.
A Home Office spokesman said: "Each case is considered in accordance with the immigration rules."
William Culver-Dodds, the chief executive of Harrogate International Festival, admits that when he chose the line-up of this year's festival, he decided to avoid certain acts, including African performers who were most likely to face visa problems.
Mr Culver-Dodds said: "When engaging artists for the festival, it was in the back of my mind where they were coming from and whether we would actually have difficulties.
"This year, we have avoided some countries because of the issues we might have, and this is a growing worry for me. Last year, it took quite a while to get Senegalese Youssou N'Dour to the festival, and we are aware it will become increasingly difficult to arrange visas.
"It's always incredibly difficult working with African artists because of the logistics of where they go to get their visas."
In the case of Mapfumo, who performed at Live8's Eden Project event in Cornwall last year - his record label, Real World Records, and the organisers of Womad issued a statement to express their dismay.
It said: "Thomas Mapfumo has been refused a visa to enter the UK, despite having been issued with UK work permits. The reasons given for this are that he entered the US on a 'P visa' granted to musicians but then changed this by applying for political asylum. Based on that, the entry clearance officer at the British Embassy is not satisfied that he intends to leave the UK."
A Real World Records spokeswoman added that visa refusal on a technicality could prove "very detrimental for musicians' careers". "It is worrying. People could be reluctant to book you, and it could have a knock on effect," she said.
Simon Broughton, the editor of the world music magazine Songlines, said it would also prove problematic for promoters. "The promoters often take a risk with bands which are not well known here," he said. "It's difficult enough to raise interest and the profile of the bands without visa problems."