LONDON, June 15 (Reuters) - At London"s Dominion theatre, "The Prince of Egypt" cast rehearse a dance weeks ahead of the show"s re-opening. The musical welcomes back audiences on July 1 with social distancing - measures big West End productions had hoped would end next week so that they could re-open fully but have now been postponed by a month. "We are very fortunate that we have a very large auditorium and we are able to go ahead with a socially distanced audience," producer Neil Laidlaw told Reuters. "But for most of the industry, it was very disappointing." On Monday, British Prime Minister Boris Johnson delayed plans to lift most remaining COVID-19 restrictions from June 21 to July 19, citing the spread of the more infectious Delta variant. The news was another hit to London"s West End theatres forced to close last year because of the global pandemic. In May, some re-opened with smaller productions and at 50% capacity. "A four-week delay to the theatre world is pretty much disastrous for a lot of people," Julian Bird, chief executive of the Society of London Theatre and UK Theatre, said. "A lot of producers, a lot of theatres have to make plans and change things. Most crucially what we need ... is that commitment from the government that this won’t be extended again." Social distancing is not financially sustainable for major musicals, most of which planned summer re-openings. "This delay is yet another bungle from a government that wouldn"t be given a single star in a review of its performance," Howard Panter and Rosemary Squire, whose Trafalgar Entertainment aimed to re-open musical "Jersey Boys" in late July, said in a statement. "The confusion and muddled-messages are reminiscent of a West End farce." Last week, veteran composer Andrew Lloyd Webber, whose new "Cinderella" musical soon begins performances, vowed to reopen his London shows without social distancing even if it meant risking arrest. On Monday, Johnson said the government was in talks with Webber "to try to make it work", suggesting "Cinderella" could be part of a pilot event scheme, a statement the composer tweeted he was "pleased & surprised to hear". For "The Prince of Egypt", shows will be socially distanced for the first two months and planned for full capacity from early September. "We"re in show mode. We"re ready," actor Liam Tamne, who plays Ramses, said. "But of course, in the back of our minds, we were always thinking, can it be pulled away from us?" Reporting by Mindy Burrows; Additional reporting by Marie-Louise Gumuchian and Sophie Royle, Editing by Alexandra Hudson