LONDON — Back in 2017, London music fans had high hopes for a reinvigoration of the city’s classical music scene.

That year, Simon Rattle, one of the world’s most acclaimed conductors, became the music director of the London Symphony Orchestra, and Diller Scofidio & Renfro, the architects behind the High Line in New York, were appointed to design a world-class 2,000-seat concert hall in the city.

Now, the situation couldn’t be more different.

On Thursday, just weeks after Rattle announced he would leave London in 2023 to take the reins at the Bavarian Radio Symphony Orchestra in Munich, London officials announced that plans for the new hall had been scrapped. Rattle had been the driving force behind the project.

In a news release announcing the decision, the City of London Corporation, the local government body overseeing the proposal, did not mention Rattle’s departure; the new hall would not go ahead because of the “unprecedented circumstances” caused by the coronavirus pandemic, the release said.

The announcement was not unexpected. Few private funders came forward for the project, and Britain’s government was reluctant to back the project, which critics had decried as elitist, after years of cuts to basic services.

But some musical experts say the news is still a blow to Britain’s classical musicians, already suffering from a pandemic-induced shutdown of their work, and Brexit, which has raised fears about their ability to to perform abroad.

“It’s a further confirmation of the parochialization of British music and the arts,” said Jasper Parrott, a co-founder of HarrisonParrott, a classical music agency, in a telephone interview.

The mood among musicians was low, Parrott said, especially because of changes to the rules governing European tours that came about because of Brexit. Before Britain left the European Union, classical musicians and singers could work in most European countries without needing visas or work permits, and many took last-minute bookings, jumping on low-cost flights to make concerts at short notice.

Classical musicians now require costly and time-consuming visas to work in some European countries, Parrott said. Changes to haulage rules also make it harder for orchestras to tour, he added: Trucks carrying their equipment are limited to two stops on the continent before they must return to Britain.

Deborah Annetts, the chief executive of the Incorporated Society of Musicians, said on Tuesday during a parliamentary inquiry into the new rules that she had been “inundated with personal testimony from musicians as to the work that they have lost, or are going to lose, in Europe as a result of the new visa and work permit arrangements.”

A British musician who wanted to play a concert in Spain would have to pay 600 pounds, or about $840, for a work permit, she said, adding that this would make such a trip unviable for many. She called upon the government to negotiate deals with European countries so cultural workers could move around more easily.

Parrott said he expected many British classical musicians would retrain for other careers, or move outside Britain for work, if the rules were not changed.

High profile departures like Rattle’s have only contributed to the impression of a sector in decline. On Jan. 22, Mirga Grazinyte-Tyla, a young Lithuanian conductor seen as a rising star, announced she would leave her post as music director of the Birmingham Symphony Orchestra at the end of the 2021-22 season. “This is a deeply personal decision, reflecting my desire to step away from the organizational and administrative responsibilities of being a music director,” she said in a statement at the time.

Manuel Brug, a music critic for Die Welt, the German newspaper, said in a telephone interview that, viewed from the continent, classical music in Britain seemed in a bad way, “with all this horrible news.”

The new London concert hall “was always a dream, but at least it was a dream,” he said.

Given recent developments, many British musicians and singers may have to consider moving to Europe if they wanted to succeed, he said.

Yet not all were downbeat about the future. British musicians could cope with the impact of the coronavirus, or Brexit — but not both at the same time, unless the government stepped in to help, said Paul Carey Jones, a Welsh bass baritone who has campaigned for the interests of freelance musicians during the pandemic.

“British artists are some of the best trained, most talented and most innovative and creative,” he said. “But what we’re almost completely lacking is support from the current government. So we need them to grasp the urgency of the situation.”