The makers of 'Mr. and Mrs. Smith' struggled to develop a script for a possible sequel.

Brad Pitt and Angelina Jolie starred in the 2005 action-comedy movie - which proved to be a huge hit at the box office - and screenwriter Simon Kinberg has now revealed why a sequel never materialised.

Simon, 50, told JoBlo.com: "The strength of the first movie is it’s a love story; they are, you know, falling back in love with each other or in love for the first time in a genuine way. And to tell a love story, to serialise a love story is very hard. Because no matter what you do in the second movie, sure, they could be partners and spies and bickering together, but you wouldn’t actually have the arc of two people who are falling in love."

The movie grossed almost $500 million at the worldwide box office.

The project also helped to establish Brad and Angelina's personal relationship, which turned into a five-year marriage.

The 48-year-old actress - who was married to Brad between 2014 and 2019 - was initially keen to star in a sequel.

However, the screenwriters struggled to create something "original".

Angelina previously told MTV News: "We did ask somebody to look into 'Mr. and Mrs' to see if they could crack a sequel, but there wasn’t anything original. It was just, ‘Well, they’re going to get married, or they’ve got kids, or they get separated.’ Never great."

Angelina also suggested that their real-life romance complicated the idea.

She shared: "I don’t think people want to see people who are really together intimate onscreen."