Aside from members of his family, Felix Mendelssohn’s closest lifelong friend was Carl Klingemann (1798–1862). Eleven years older than Mendelssohn, Klingemann was born in Limmer an der Leine, near Hanover, the son of the local cantor and schoolmaster. Academic aptitude led to a diplomatic career in the service of the King of Hanover, and in 1818 he was posted to the Hanoverian Embassy in Berlin, where by 1823 he had entered the Mendelssohn family’s circle. His literary and musical interests, combined with his sense of humour, soon made him a favourite of all the family. For a while he even rented an apartment in the Mendelssohns’ Leipzigerstrasse house, before he was sent to London in 1827, where he was to remain for the rest of his life. Initially a clerk at the Hanoverian Chancellery, he was promoted to secretary in 1837 just before the Chancellery became an Embassy on the separation of the British and Hanoverian thrones; further promotion to Legationsrat followed around 1856. On Mendelssohn’s ten visits to Britain, Klingemann was thus a natural associate, and on many of these occasions the composer lodged with him. Indeed, it was Klingemann’s presence in London that was probably a major factor in the decision to make England the first destination of the three-year European tour that Mendelssohn began in 1829. It is really this first visit that brings Klingemann’s name to notice in Mendelssohn biographies, since, following the London musical season, the two friends embarked on their famous tour to Scotland, which Mendelssohn recorded in pencil drawings with accompanying verses by Klingemann. When they were apart, they corresponded regularly, and from the beginning of 1835 they agreed on a regular monthly exchange of letters, Mendelssohn writing at the beginning and Klingemann in the middle of the month. Although from time to time one or other failed in his duty, the plan was basically maintained for the rest of Mendelssohn’s life. As a result 157 letters from Mendelssohn and 154 from Klingemann are extant, easily the most substantial of the composer’s correspondence outside his family. Klingemann died in 1862, just as a flood of publication of letters and memoirs of Mendelssohn was getting under way. Even if he had lived, however, it is most unlikely that he would have contributed to them. For Klingemann, Mendelssohn’s friendship was a private affair, not to be shared with the world. Although his widow, Sophie, encouraged by Friedrich Chrysander (who had already approached Carl before his death), did initially look favourably on publication of the letters, she was dissuaded by Felix’s brother, Paul, and any publication of their correspondence remained in abeyance until Klingemann’s eldest son, Karl, finally edited Felix Mendelssohn Bartholdys Briefwechsel mit Legationsrat Karl Klingemann in London in the Mendelssohn centenary year of 1909. The introduction included an account of his father’s life, and it has remained a principal source of information on Klingemann and his relationship with Mendelssohn up to the present day, albeit one subject to filial piety. The edition included almost all the composer’s letters (149 out of 157), but only forty-nine of the 154 that Klingemann wrote, though Karl junior does not mention this. Mendelssohn’s letters are presented complete, whereas many of those of Klingemann that are included are abbreviated, albeit with omissions indicated. Compared to many earlier publications of Mendelssohn’s letters, the transcriptions proved fairly reliable, and this has led scholars to overlook the lack of so much of the other half of the correspondence. As Regina Back points out, it has resulted in several cases of missed evidence, which the present volume valuably corrects. It is quite understandable that in 1909 Karl junior should have considered Mendelssohn’s own letters to be of greater importance than his father’s for the anticipated readership, especially as much of the content of the omitted material consists of Klingemann bringing Mendelssohn up to date on the London political and social scene.