Blake Lively says the key to a happy marriage is to "marry your best friend"

She told HELLO! magazine: "Honestly, my husband and I are best friends. Marry your best friend."

Along with her husband, Blake also has another famous best friend, Taylor Swift, who she worked with on her new movie 'It Ends With Us'.

Blake revealed that the pop superstar gave permission for her song 'My Tears Ricochet' to appear in the movie, despite the film having "virtually no budget".

Blake said: "We had virtually no budget so there were a lot of favours asked. Taylor is one of those friends who always shows up for you and I am so grateful to her for how she worked with us.

"I'm really proud of the soundtrack on this movie and Taylor is definitely a big part of that. Her music and lyrics are perfect."

Blake worked as a producer on the film - which is adapted from Colleen's Hoover's bestselling novel - and she is "so proud" of it.

She said: "I'm so excited about bringing this story to life. It's such an emotionally rewarding film and I'm so proud of it. It is a huge responsibility to do something like this.

"Everyone's vision of the characters in a book is different so it's impossible to please everyone. It's scary to take that on but I honestly didn't feel scared."