By now Beethoven's hearing had again seriously deteriorated, necessitating Beethoven and his interlocutors writing in notebooks to carry out conversations. These 'conversation books' are a rich written resource for his life from this period onwards. They contain discussions about music, business and personal life; they are also a valuable source for his contacts and for investigations into how he intended his music should be performed, and of his opinions of the art of music. His household management had also improved somewhat; Nanette Streicher, who had assisted in his care during his illness, continued to provide some support, and he finally found a skilled cook. A testimonial to the esteem in which Beethoven was held in England was the presentation to him in this year by Thomas Broadwood, the proprietor of the company, of a Broadwood piano, for which Beethoven expressed grateful thanks. He was not well enough, however, to carry out a visit to London that year which had been proposed by the Philharmonic Society. Despite the time occupied by his ongoing legal struggles over Karl, which involved continuing extensive correspondence and lobbying, two events sparked off Beethoven's major composition projects in 1819. The first was the announcement of Archduke Rudolf's promotion to Cardinal-Archbishop as Archbishop of Olomouc (now in Czechia), which triggered the "Missa Solemnis" Op. 123, intended to be ready for his installation in Olomouc in March 1820. The other was the invitation by the publisher Antonio Diabelli to fifty Viennese composers , including Beethoven, Franz Schubert, Czerny and the 8-year old Franz Liszt, to compose a variation each on a theme which he provided. Beethoven was spurred to outdo the competition and by mid-1819 had already completed 20 variations of what were to become the 33 "Diabelli Variations" op. 120. Neither of these works were to be completed for a few years. A significant tribute of 1819, however, was Archduke Rudolf's set of forty piano variations on a theme written for him by Beethoven (WoO 200), and dedicated to the master. Beethoven's portrait by of this year, which was one of the most familiar images of him for the next century, was described by Schindler as, despite its artistic weaknesses, "in the rendering of that particular look, the majestic forehead ... the firmly shut mouth and the chin shaped like a shell, ... truer to nature than any other picture."