Director steps into singer's shoes Members of the audience were told of the arrangement before the performance started and offered vouchers to the value of their tickets if they wanted to leave. Only around 100 out of an audience of more than 2,000 took up the offer, according to ROH spokesman Christopher Millard. Andrew Neil, the broadcaster and former newspaper editor, tweeted: "Cosi Fan Tutte at #roh. Thomas Allen (Alphonse) taken suddenly ill. So someone sings offstage while young chap acts the part! Last night Mr Millard said: "Thomas Allen is not very well and he had to cancel quite late this afternoon. He is an amazing, top-flight opera singer and he is not easily replaceable. We were not able to get somebody to be there on time for the performance to begin. We had another singer who was in a production which opens tomorrow, The Marriage of Figaro, and he has sung it. He knows the part. He has not been in this production. It is quite complicated in terms of the acting part of the role so we decided what we would do would be, to have the director on stage, and the singer was standing on the side of the stage, so he is visible to the audience. He said it was "fairly common" for such arrangements to take place in operas when singers were unwell or lost their voice. People will do their utmost to try and fulfil their role but unfortunately he was not feeling well enough to do it. You can't expect a replacement to arrive and just do it. Rather than cancel the whole thing, we informed people of the fact that this was happening so hopefully they would stay and enjoy this rather extraordinary evening. We made an announcement from the stage and explained the circumstances and anybody who felt they didn't wish to stay was offered an opportunity to receive a voucher to the value of the ticket. There were people who decided to leave and I reckon that was probably about 100. Sir Thomas has taken on the role of Don Alfonso to acclaim in the past, with a recent review hailing his "dangerously charming" performance. He made his debut with the Royal Opera with Billy Budd and was soon appearing in The Marriage of Figaro, Don Giovanni and Cosi fan tutte and there were further roles in Die Fledermaus and The Mastersingers of Nuremberg. In 1989, he became a CBE and ten years later he was knighted. The singer, born in Seaham, County Durham, was said to have been the inspiration for the character of Billy Elliot - a boy from the North East who pursues his dream of becoming a dancer.