The Dutch lexicographer Hans Westgeest theorizes the hidden theme to Elgar's Enigma Variations originates from the second movement of Beethoven's Pathétique Piano Sonata. His thesis precipitously rests almost exclusively on a conversation between Elgar and August Jaeger, the inspiration behind Variation IX Nimrod. In September 1898 Elgar was feeling so dejected he vowed to abandon music altogether. Jaeger lambasted Elgar’s ingratitude for his tremendous musical gift, invoking Beethoven's example of persisting to produce great music in the face of many worries and setbacks. Jaeger followed up this discussion with a scathing letter to which Elgar penned a conciliatory and appreciative reply. Much later in 1927, Elgar furnished written comments for a set of pianola rolls published two years later in 1929. Concerning Variation IX he wrote it was "the record of a long summer talk, when my friend discoursed eloquently on the slow movements of Beethoven…it will be noticed that the opening bars are made to suggest the slow movement of the Eighth Sonata (Pathétique)."
The Power of Suggestion
The whiff of suggestion should not be mistaken for the pleasing perfume of a genuine solution. Elgar made those very close to him swear never to disclose the secret. When Dora Penny wrote to Jaeger asking him for the answer, she received the following reply:
Now, Dorabella, you must be a good girl and not ask me about that. I do not suppose that I could keep it from you if you were to plead with me, but the dear E.E. did make me promise not to tell you. 
During his lifetime the identity of the unstated Principal Theme was a closely guarded secret, so what reasonable explanation could there be for Elgar surrendering the answer so publicly in his notes for the pianola rolls? The short answer is there is no credible explanation. What is known with complete confidence is Elgar took the secret to his Enigma Variations to the grave. Like other prominent Elgar scholars, Westgeest readily concedes this point: “Of course, there can never be a hundred percent guarantee that a particular solution is correct and the one solution intended by Elgar, because the composer died without revealing it.” If the solution were indeed Beethoven’s Pathétique, Elgar openly volunteered it in his notes for the 1929 pianola rolls. Either Elgar kept the answer to himself, or he disclosed it – Westgeest cannot have his proverbial cake and eat it too. Ultimately the Pathétique theory is completely out of character for Elgar since he consistently refused to confirm any solution during his lifetime. This point alone is sufficient to discard Westgeest's theory, yet there is more to consider in debunking this problematic solution.
The accuracy of the pianola rolls is one weakness to consider in assessing the strength of Westgeest’s theory. By 1927 Elgar was bound and determined to safeguard the secrets of the Enigma Variations. If enigma sleuths could not be deterred by his repeated and emphatic denials, then they could certainly be frustrated by disingenuous and misleading statements sprinkled into his commentary. One notorious example is his comment regarding the secret dedicatee of Variation XIII. For the original 1927 note Elgar wrote, “The asterisks take the place of the name Lady Mary Lygon.”  However, this statement was altered to read for the 1929 pianola rolls, “The asterisks take the place of a lady who, at the time of the composition, was on a sea voyage.”  Lady Lygon was not on a sea voyage when the Variations were composed, safely ruling her out as the secret friend. In April 1899 he openly dedicated Thee Characteristic Pieces to Lady Lygon without resorting to some mysterious veil of secrecy. Since he was deliberately coy in his description of Variation XIII, it is equally likely his comments on Variation IX were designed to mislead investigators into suspecting the hidden melody was Beethoven’s Pathétique Sonata. Such a candid admission would be entirely out of character for Elgar who spent his life consistently denying any alleged solution to even to his closest friends.
There are numerous examples of Elgar’s steely intransigence in the face of friends anxious for the secret to the Enigma Variations. Dora Penny – the Dorabella of Variation X – repeatedly begged him to divulge the answer. During one of these encounters, Elgar replied, “Oh, I shan’t tell you that, you must find it out for yourself.” She insisted, “But I’ve thought and racked my brains over and over again.” He responded, “Well, I’m surprised. I thought that you of all people would guess it.”  He was clearly humoring himself at her expense while reaffirming the very same point made in the original 1899 program note – the solution must remain "unguessed." Westgeest’s theory is essentially nothing more than a guess, and Elgar made is perfectly clear that guessing would not suffice. There must be more to the puzzle than nebulous approximations. Another friend who guessed unsuccessfully was Troyte Griffith, the inspiration for Variation VII. He once suggested God Save the King, and Elgar replied, “Of course not, but it is it is so well-known that it is extraordinary no-one has found it.”  Considering that Elgar was stubborn enough to resist giving the answer away even to his closest friends, there is no rationale for believing he would step out of character and give the answer away to a world of strangers. More decisively, Westgeest’s "solution'"fails to satisfy specific conditions given by the composer regarding the unstated Principal Theme.
A Conditional Theme
A credible case can be made for that candidate theme only if it can be shown to effectively satisfy six conditions Elgar gave describing the relationship between the Enigma Variations and the covert principal Theme. Secured directly from Elgar’s recorded words by multiple, independent, unimpeachable sources, those six conditions are:
1. The Enigma Theme is a counterpoint to the principal Theme.
2. The principal Theme is not heard.
3. The principal Theme is famous.
4. Fragments of the principal Theme are present in the Variations.
5. The principal Theme is a melody that can be played through and over the whole set of Variations including the entire Enigma Theme.
6. The Enigma Theme comprises measures 1 through 19.
Any theme that violates just one of those six conditions must be ruled out as invalid.
A Pathetic Theory
The first and foremost test is to play a candidate melody “through and over” the Enigma Theme to assess whether there is credible evidence for contrapuntal and horizontal fit. Before mapping a prospective melody above the Enigma Theme, it is first necessary to transpose it into the corresponding major and minor modes of G. These alterations between the major and minor modes are necessitated by structure of the Enigma Theme which opens in G minor (measures 1-6), continues in G major (measures 7-10), returns to G minor (measure 11-16), cadences in G major (measure 17), and modulates back to G minor in the bridge leading to Variation I (measures 18-19). Even when granting these generous accommodations to facilitate a contrapuntal mapping, the melody from the second movement of Beethoven’s Pathétique Sonata fails to play even one full cycle over the Enigma Theme. Westgeest's alleged solution sounds as incongruous as it looks, ultimately falling short (and flat). He may be adept at making maps, but Westgeest is inept at mapping counterpoints. An unrelenting barrage of howling dissonances seals the case against Beethoven's Pathétique as a viable candidate for the missing melody to the Enigma Variations.
Since it does not cleanly overlay the Enigma Theme, the second movement from Beethoven’s Pathétique Sonata cannot conceivably be the covert Theme to the Enigma Variations. Westgeest's alleged "solution" melody does not fit, thereby rendering it unfit. More striking still is the fact Beethoven’s Pathétique is not even a clear and convincing counterpoint to Nimrod. There is a far more compelling theme that plays "through and over" Nimrod that is so self-evident that it makes the genuine melodic solution to the Enigma Variations as plain a pikestaff.
The only theme to successfully satisfy Elgar’s six specific conditions is Ein feste Burg (A Mighty Fortress) by Martin Luther. A precise vertical and horizontal alignment between the two melodies is realized by Elgar's sophisticated treatment of Ein feste Burg as a retrograde counterpoint in an augmented form. Such an unconventional approach accounts for the profound difficulty in detecting a contrapuntal alignment because researchers invariably pair the beginning of a prospective melody with the beginning of the Enigma Theme. Such a predictable approach produces a mismatch even when the correct melody is considered.
The case for Ein feste Burg as the covert Principal Theme to the Enigma Variations is extensive and persuasive. Confirmation that Ein feste Burg is the hidden theme is given by a diverse range of music ciphers in the Enigma Theme and Variation XIII. Within the Enigma Theme is concealed a music box cipher, Elgar’s "dark saying" linked to the Enigma mentioned in the original 1899 program note. Incredibly, Elgar did not take his secret to the grave, but rather enciphered the answer within the orchestral score to ensure its survival and organic connection to the work. When discovered, the decrypted answer would remain unguessed just as Elgar predicted. He even went so far as to encode the initials for the hidden melody in the Enigma Theme which modulates between the minor and major modes of G. It is hardly coincidental that the accidentals for those two keys (E flat, F sharp, B flat) furnish the initials for Ein feste Burg. An alphanumeric cipher concealed within the Mendelssohn fragments also encodes those same initials.
The odd nickname for Jaeger’s Variation (Nimrod) is linked to the title A Mighty Fortress by of one Elgar’s favorite pastimes, wordplay. When he gave a copy of Longfellow’s novel Hyperion to the conductor Hans Richter following the premiere, Elgar literally gave away the answer. No wonder he suspected the solution would soon be discovered. Even the wrong date on the original score is a revealing clue since it falls on the anniversary of Luther’s death. To learn more about the secrets of the Enigma Variations, read my eBook Elgar’s Enigmas Exposed. Like my heavenly Father’s gift of salvation, the price is free.
 Turner, Patrick. Elgar's 'Enigma' Variations - a Centenary Celebration. London: Thames Publishing, 1999, p. 68
 Rushton, Julian. Elgar: Enigma Variations (Cambridge Music Handbooks). New York: Cambridge University Press, 1999, p. 46
 Turner, Patrick. Elgar's 'Enigma' Variations - a Centenary Celebration. London: Thames Publishing, 1999, p. 63
 Ibid, p. 68
 Ibid, p. 69
 Ibid, p. 69
 Powell, D. M. (1947). Edward Elgar: Memories of a variation (2nd ed.). London: Oxford University Press, p. 23
 Ibid, p. 119