'I will always be yours, with endless devotion,' he typed, in one of the last epistles of a correspondence which lurched between lacrimony and acrimony.
Now, two months after Dietrich's death in Paris, the letters are included in a sale of English literature and history at Sotheby's on 21 July (11am). The pre-sale estimate is pounds 1,200- pounds 1,500. Mr Benedict, a well-bred Hungarian emigre, Sorbonne graduate in languages, US Army instructor in photography during the war and former member of the film producer Joe Pasternak's staff at Universal Studios, was no match for Lola-Lola of The Blue Angel. She sucked him dry and spat out the pips.
When he became her manager he weighed a jovial but ingratiating 18 stone, boasting that he was accepting only the best contracts for her solo performances and earning from her such typewritten bouquets as: 'You did all the work and never left me and cared for me like a brother.' After two years of threshing in the shark-infested waters of American show business, he had lost four stone, been fleeced by Dietrich's entourage and had his car repossessed.
Dietrich started the 1973-74 period - something of a forgotten epoch, judging by her own autobiography - as a living legend with a looming but still-distant sell-by date, anxiously cosseting her mystique both on and off the stage. Then aged 69 (or was it 72, or even 73?) she contemptuously turned down one-night stands, insisted on a rest day and a rehearsal day before each appearance, and stipulated free travel and hotel accommodation for her and her entourage of six (mainly musicians).
By the time Michael Benedict was dispatched, she had spent six months or more in a wheelchair after falling into the orchestra pit and gashing a leg during a performance in Washington. The fall came hours after she had written upbraiding him for the punishing tour schedule - but, to make ends meet, she pressed ahead with another four-month tour, agreeing to as many as seven shows in five days at some stopovers, using a ramp so she could be wheeled on stage.
Meanwhile, as the correspondence shows, she was being rejected as an advertising icon by Busch, Budweiser and Heineken beers, and the Chromalloy customised marketing corporation was unimpressed by 'The Marlene Dietrich Way', a range of vitamins, minerals, health foods and cosmetics dreamt up by Mr Benedict.
Dietrich was a tyro at the portable typewriter, dashing off eagle-eyed complaints to Mr Benedict whenever she suspected that an agent or producer or her own entourage were trying to rip her off - which was practically all the time. Marlene Dietrich Inc was very much a one-woman band: she had no one to protect her but herself. Indeed, such was the chicanery which threatened to engulf her, the letters reveal, that it is difficult to imagine how she summoned the energy to appear on stage at all.
She was as steely as her film heroines. When a promoter supplied four violinists too few - her standard contract stipulated a 23- piece house orchestra with nine violins - she hit the roof.
'. . . We never, but never had only five violins,' she wrote to her American agent Frank Rio: 'Any promoter who can afford me will not stop at ONE VIOLIN less.'
Mr Rio was one of the small fry who routinely tasted steel whenever they transgressed. She wrote to Mr Benedict in her less-than- perfect English: 'If Frank Rio will not give you an advance of dollars 2,000 on a tour which will bring a total of dollars 123,000, then I don't understand even less.'
She ordered her conductor, Stan Freeman, to make his own travel reservations 'just to be sure he pays for his extras'. Her most fearsome letters are studded with 'This is final]'
Mr Benedict framed the letter to him in which she refused to present the Academy Awards: 'I have the lowest regard for that organisation . . . they can go on doing without me.'
But, again like her film persona, she was cut to the quick whenever friends betrayed her. Plenty did. She wrote to Mr Benedict that she had been 'stunned beyond belief' upon being told by him that Al Sendry, an old friend, had claimed a 'finder's fee' for making a personal introduction for her.
Her usual salary for up to eight appearances at any one spot on tour was dollars 25,000 plus a percentage of the gate. Her scribbled note to Mr Benedict shows she was cute enough to know that some managements would stump up her dollars 25,000 a day early - but that gate takings below an agreed minimum would mean no added percentage. Mr Benedict got 5 per cent of her gross and she made him earn it. He never sweated so much as when she played cat and mouse with a contract which he, in his inexperience, had as good as agreed to.
'Marlene, please try to understand me,' Mr Benedict wrote plaintively while scheduling her second tour, including New Orleans, in 1974. 'This contract has been negotiated for the very best period this hotel has each year, just prior to the Mardi Gras . . . They are counting on you and I don't know how to approach them with your decision to do only one week. They are spending dollars 10,000 just so that your every wish is obeyed . . .' ending with the ritual: 'I hope you know that to me, only one person counts, and that is you. All else is secondary.'
Marlene was used to being obeyed. An internal memo by her staff on the occasion of her stay at the Fairmont Hotel, San Francisco, in March 1974, says: 'Mr Mikulak (hotel manager) has made it very clear to me that Miss Dietrich gets what she wants.'
What she always wanted was a two-bedroom hotel suite shared with her secretary Ginette Vachon, and a king-size bed in each room; then extra racks for her 36 pieces of luggage, 'enormous amounts' of wardrobe space, a private telephone line with a 25ft cord, Dom Perignon champagne 'by the case', six bottles of Heineken beer in the refrigerator, white and yellow flowers, a salt-free diet, sardine and onion sandwiches on rye - and her salary cheque paid before the last show on the last day of her engagement. All this, and a lift and security man for her wheelchair.
Her promoters had to obey, too. She was hot on lighting. It went wrong in Montreal, robbing her of her dramatic entrance. 'At the end of the overture, which by now you know is very abrupt', her overworked typewriter rapped out, 'there must be a complete black- out except for the music stand lights. The announcer's voice takes place during this blackout. After the word 'Dietrich' you count to 3 (three) and give the signal to the spotlight man . . .'
Even the audience had to obey. She wrote her own 'claque list' of cues to encourage laughter and applause. Her most famous song, 'Lili Marlene', was to have 'applause after first sentence' and 'whenever you hear 'Blue Angel' you applaud'.
But in May 1974, with one week to go of the second tour, a promoter in Minneapolis was complaining that he was looking at a dollars 7,000 loss, that the act lacked 'drawing power' and that he had had to put up posters in every gay bar in Minneapolis and St Paul.
If the writing was on the wall for Dietrich, it was on the wall for Mr Benedict, too. He had cooked his goose on the first tour by arranging for her a four-hour drive into Washington followed by a performance without dress or light rehearsal, followed by an 11am contract signing and press interview 'to help ticket sales'. It was one of the more monumental of his many gaffes. 'You don't know this business at all,' her typewriter raged.
At that night's performance, worn out, she fell into the pit, suffering, according to a doctor's report the following day, 'a severe avulsed laceration of the lateral aspect of the lower third of the left leg which measured about 10 by 5cm'. The report advised a fortnight's rest, to 'preserve a viable skin flap'.
Mr Benedict proffered: 'Nothing in this world matters to me at this time except your health and complete recovery, your happiness and contentment', adding 'there was no possible reason for me to say that the hotel bills would be paid in Montreal . . . Please don't be angry with me, remember that I love and worship you.'
That was another of his undoings - failing to win contracts agreeing free hotel accommodation, being afraid to admit it to her, then having to pay for it (plus additional out-of-contract days in hotels freeloaded by the entourage), first out of his own pocket, then out of hers. Broke, he finally succumbed to charging his own extra hotel days to her, a trick she could spot a mile off.
Dietrich, at her steeliest, stopped Mr Benedict's salary. 'That you could not even behave correctly this last time is astounding. Don't come to me with any stories contradicting my assertions.' He wrote back, of course. 'Kill me as you promised me. Yes, I will miss you terribly . . . but I will just have to survive, like I am surviving without my mother . . . Please find the dollars 20 enclosed you loaned me yesterday.'