You might assume a biopic would be the easiest film to make. After all, the story is already written, the character already exists for the actor to inhabit, and in most cases the awards are almost guaranteed. However, it can be very, very easy to produce a shoddy product because directors and writers fail to understand the basic rules of the biopic.

These are not documentaries. A biopic needs to embellish real life events and people for dramatic effect, in order to tell a more subjective story about the main character. Historical verisimilitude is not important in these films; what matters is story and character.

Legend (2015) suffers greatly because it lacks these crucial elements. While on paper a biopic about the infamous Kray twins should work, in practice the film falls flat. This is mostly due to the construction of the story. The film focuses on the Kray’s career as criminals, their relationship as brothers, Ronnie Kray’s (Tom Hardy) mental illness and Reggie Kray’s (also Hardy) relationship to Frances Shea (Emily Browning), his wife. There are too many elements to this film, which leaves a lot of it under-developed and unsatisfying. This is partially due to the time scale and the film having too broad a time frame. Similarly, the use of narration from Shea’s perspective seems strange ,especially at the end.

This is a common problem with biopics as at times they can feel over-full, and this is certainly the case of the 2010 Ian Dury biopic, Sex & Drugs & Rock & Roll, and 2015’s Black Mass. A biopic should have a singular focus, like in 2005’s Walk the Line, where the relationship between Johnny Cash (Joaquin Pheonix) and June Carter (Reese Witherspoon) is at the forefront, while Cash’s career is in the background.

You can’t make a biopic based on just anyone. Take for example William and Kate (2011). This boring film failed because of an uninteresting story, a lack of struggle, and an inherent lack of good characters, which is a fatal flaw. Rock stars are so popular in this genre usually because they have an element of self-destruction that makes them so appealing to watch. It is also partly due to the actors playing them. With Walk the Line and Sex & Drugs & Rock & Roll, casting is perfect, physically and emotionally, with the audience believing that Pheonix is Cash and Serkis is Ian Dury because they look and act like the people they’re playing. Having said that, the actor doesn’t necessarily have to physically resemble the character they are playing, as is the case with Colin Firth who gives such an emotional performance in The King’s Speech that despite his looks, the audience is convinced.

Ultimately, a biopic’s main function is much like that of a fictional film; it must entertain an audience through its story and characters, and the fact that these are real people and the story actually happened is mere coincidence.

Accuracy and detail are the enemy; these are tales of emotion first, not history.