in London, Lind appeared in most of the standard opera repertory. In early 1849, still in her twenties, Lind announced her permanent retirement from opera. Her last opera performance was on 10 May 1849 in Robert le diable; Queen Victoria and other members of the Royal Family were present. Lind's biographer Francis Rogers wrote, "The reasons for her early retirement have been much discussed for nearly a century, but remain today a matter of mystery. Many possible explanations have been advanced, but not one of them has been verified". Lind and Mendelssohn In London, Lind's close friendship with Mendelssohn continued. There had been claims that their relationship was more than friendship. In 2013, George Biddlecombe confirmed in the Journal of the Royal Musical Association that "The Committee of the Mendelssohn Scholarship Foundation possesses material indicating that Mendelssohn wrote passionate love letters to Lind entreating her to join him in an adulterous relationship and threatening suicide as a means of exerting pressure upon her, and that these letters were destroyed on being discovered after her death". Mendelssohn was present at Lind's London debut in Robert le diable, and his friend, the critic Henry Chorley, who was with him, wrote: "I see as I write the smile with which Mendelssohn, whose enjoyment of Mdlle. Lind's talent was unlimited, turned round and looked at me, as if a load of anxiety had been taken off his mind. His attachment to Mademoiselle Lind's genius as a singer was unbounded, as was his desire for her success." Mendelssohn worked with Lind on many occasions and wrote the beginnings of an opera, Lorelei, for her, based on the legend of the Lorelei Rhine maidens; the opera was unfinished at his death. He composed the soprano aria in his oratorio Elijah ("Hear Ye Israel") with Lind's voice in mind, focusing the tessitura of the aria around F-sharp (F♯5), a note in her range that Mendelssohn supposedly found irresistibly charming. Four months after her London debut, she was devastated by the premature death of Mendelssohn in November 1847. She did not at first feel able to sing the soprano part in Elijah, which he had written for her. She finally did so at a performance in London's Exeter Hall in late 1848, which raised £1,000 to fund a musical scholarship as a memorial to him; it was her first appearance in oratorio. The original intention had been to