An East Coast liberal, Bernstein was uneasy about England and its imperialist past. He loved Gilbert and Sullivan operettas and the Listener magazine's crossword puzzles but had hated his first visit to London in 1946. On that occasion (arranged by the music publisher Ralph Hawkes, a friend of his mentor Aaron Copland), Bernstein had conducted the London Philharmonic in six concerts and the newly formed Philharmonia for a recording of Ravel's G Major Piano Concerto that was sufficiently problematic to never be issued in the UK. Bernstein had been ill, lonely, depressed by bomb-ravaged London and unimpressed by the quality of its orchestral musicians. Over the next three decades his London concerts (apart from appearances with the New York Philharmonic on various tours) had all been given with the adventurous London Symphony Orchestra, including a memorable Mahler Eight at the Royal Albert Hall in 1966 and a Stravinsky memorial concert in 1972. For the BBC Symphony Orchestra it was therefore something of a scoop to lure the famous maestro away from the LSO; as a regular member of Bernstein's production team for the previous decade, I was happy to serve as a go-between in the negotiations, which were concluded shortly before I retired from BBC management to concentrate on work as a director. This rehearsal film (shot in BBC TV's Omnibus studio) was one of my first assignments in my new role.

Bernstein, then sixty-three, was well aware of the historic importance of the BBC's flagship orchestra, which had been founded in 1930 under the leadership of Adrian Boult; Sir Adrian was knighted only seven years later for his achievement in establishing the orchestra as one of the UK's leading ensembles. In 1982 it was still admired as a superb instrument for the performance of contemporary music (Bernstein's new symphonic song cycle Songfest was also on the programme) but appeared much less in public than its rivals and no longer boasted such an array of distinguished solo players as in its pre-war glory days, when Arturo Toscanini and Bruno Walter had been among its guest conductors. Despite his own wealth of experience as a visiting maestro, Bernstein got off on the wrong foot with the BBC players by turning up spectacularly late for his first rehearsal, which was held in a television studio; he had done something similar with the LSO back in 1966 when he rehearsed Shostakovich's Fifth Symphony for a memorable Workshop programme. He claimed to have been driven to the wrong BBC studio but the truth was that he had underestimated the time it would take to get to White City from the Savoy ('it's just across the park') and to the despair of his assistant, he set off far too late for the traffic-clogged cross-town journey. To make matters worse, when he finally entered the studio he cut off the speech of welcome being delivered by the leader, Rodney Friend (whom he knew from Mr Friend's previous engagement as concertmaster of the NY Philharmonic), and then launched without apology for his late arrival, of which he seemed to be unaware, into a rambling discourse about his feeling of kinship for the composer whose music he was about to rehearse, Edward Elgar, whom he insisted on calling 'Eddy'. Their principal bond, it seemed, was that they shared a love of word puzzles and anagrams. Through the cameras I could see the orchestra becoming increasingly embarrassed and restless and matters did not improve when Bernstein finally began to make music: Elgar's theme was taken very slowly indeed.

In his sixties, which proved to be the last full decade of his life, Bernstein tended to take slow movements slower and fast movements faster than heretofore. His Enigma interpretation was no exception: he had a virtuoso orchestra at his disposal and he put it through its paces. When Rodney Friend complains at rehearsal that Bernstein was setting 'an impossible tempo' for 'G.R.S.' (Variation XI) the conductor points out that Tempo di molto means very fast and Friend is jokingly urged to 'be a captain' and lead his troops into battle. In truth, the fast movements are actually not excessively fast and in the splendid finale Bernstein observes Elgar's many changes of tempo with the scrupulous devotion he also paid to Mahler's instructions. He reminded his players several times that Elgar's music was in the mainstream of the European tradition, influenced by Schumann and Tchaikovsky as well as Wagner and Elgar's admiring friend Richard Strauss. He drew some exquisite playing from the soloists, notably the first clarinet, Colin Bradbury, but there were several tense moments at the rehearsal, notably when he crossed swords with the trumpet section.

There has been criticism that Bernstein makes some of the slower variations unnecessarily ponderous. In particular, his version of 'Nimrod' (Variation IX) has been held up to disbelief verging on ridicule because in performance it lasts five minutes and fifteen seconds, nearly twice as long as most conductors take it; at the first rehearsal it ran even longer, to almost seven minutes. All I can say by way of justification is that when you see the music as well as hearing it, when you watch on camera the intensity of Bernstein's beat and body language (particularly in the studio rehearsal where he implores the orchestra to 'keep it as pure and noble as you can') you are caught up in this wonderfully spiritual music: after all, Bernstein knew that Elgar aspired here to compose an adagio in the Beethoven tradition – in honour of his best friend, August Jaeger.

In a brief interview with the Omnibus presenter, Barry Norman, Bernstein is asked for his suggestion concerning the identity of the enigma of Elgar's title. At the piano he demonstrates how Elgar's theme can be combined, somewhat tortuously, with 'Auld Lang Syne'; another candidate, 'Rule Britannia', is dismissed as simply not workable as the underlying theme. For Leonard Bernstein, however, the real enigma is how a work which has echoes of so many earlier European composers should come out sounding so British, so personal to Edward Elgar: 'that is the Enigma of Genius'.