The Russo brothers. Picture: Bang Showbiz

The Russo brothers penned a letter to audiences asking them not to reveal any details of 'Avengers: Endgame' to others ahead of its release in theatres on April 26.

The acclaimed directing duo - who helmed 'Avengers: Infinity War' -penned a letter to audiences asking them not to reveal any details of the highly-anticipated film to others ahead of its release in theatres on April 26. 

The filmmakers posted the letter on Disney's official Instagram account and began the emotional message by insisting that Marvel has the "greatest fans in the world" who have "invested so deeply" in the Marvel Cinematic Universe and its characters. 

The pair said: "To the greatest fans in the world. This is it. This is the end. The end of an unprecedented narrative mosaic spanning eleven years and eleven franchises.

"For all of you who have been on this journey with us since the very beginning, sharing every high and low with your family, your friends, your classmates, your co-workers.

"Investing so deeply in every character and storyline. Laughing. Cheering. Shedding tears. Giving so freely of your thoughts and emotions in spirited dialogue, theories, fan art and fan fiction." 

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The letter went on to explain that the directors have "worked tirelessly" to come up with a surprising end to phase three of the MCU and requested that as so many fans have given their " time, hearts, and souls" to the franchise, "please don't spoil it for others". 

They continued: "Please know that the two of us, along with everyone involved in 'Endgame', have worked tirelessly for the last three years with the sole intention of delivering a surprising and emotionally powerful conclusion to the Infinity Saga.

"Because so many of you have invested your time, your hearts, and your souls into these stories, we're once again asking for you help.

"When you see Endgame in the coming weeks, please don't spoil it for others, the same way you wouldn't want it spoiled for you."