Liv Tyler's fiance thinks she is a "magical unicorn".

Liv Tyler and Kate Moss (c) Instagram

Liv Tyler and Kate Moss (c) Instagram

The 'Leftovers' actress turned 40 on Saturday (01.07.17) and her partner Dave Gardner shared a touching tribute to her on his Instagram account to mark the occasion.

He wrote alongside a picture of the actress: "Happy 40th Birthday to the most beautiful and magical unicorn, I love you so much. You are my dream girl and I am blessed to be able to call you my wife (to be) Happy Birthday Baby Girl, I love you, We all love you (sic)"

And in in a family photo of Liv, Dave, and their two children Sailor, two, and Lula, 11 months, he wrote: Happy Birthday Momma. We love you lots and lots (sic)"

The 'Armageddon' star - who also has 12-year-old son Milo with ex-husband Royston Langdon - was joined by pals including supermodel Kate Moss and actress Sadie Frost in celebrating her birthday, with a number of pictures appearing on social media showing them all having fun together over the weekend.

One picture posted on Sadie's account featured Kate sitting cross-legged outside a small tepee, while Liv grinned as she perched on the edge of a sand box.

The outdoor celebration also included a bouncy castle, with Sadie posting another photo in which she was having a great time as she jumped in the air.

She captioned the image: "I know i am suppose to be a grown up- but this was so much fun - though slightly knackering! @frost_french #floozie my Mexican inspired swimsuit @debenhams #bouncycastle #nevergrowup (sic)"

After sharing a series of other pictures from the party - including hairdresser James Brown by the pool - Sadie ended with a thank you to the birthday girl and her partner.

She wrote: "Thanks for a lovely weekend @misslivalittle @davidgardner .. couldn't have been better (sic)"

Liv had a great time at her party, and after the celebrations were over thanked Dave - who has son, Gray, 10, from his marriage to Davinia Taylor - and some of her pals for the fun weekend.

She captioned an image of herself and Dave: "my love thank you for the most wonderful birthday weekend ever !!!!! so happy. So grateful!!!! @davidgardner (sic)"

And alongside a black and white photo of herself and Kate, she posted: "Blessed for 25 years of friendship. love my girl friends !!!!! Thank you my sweet @katemossagency for the best birthday weekend ever !!!!!!!! (sic)"

In a short video clip where Liv showed off her dress - a gift from James - as she walked through the grass before Kate came crawling after her, she posted: "Splendor in the grass and along came a sexy tiger thank you for the most fun amazing beautiful birthday ever @davidgardner @katemossagency @jamesbrowncreatives (sic)"