It was a night of thrills and spills as Lauren Conrad, Heidi Montag, Spencer Pratt and Audrina Patridge walked the red carpet for the final episode of season 4 of The Hills.

Lauren sparkled in a sequin gown, while Audrina and Heidi flashed some skin in cleavage-enhancing dresses.

But the night's drama revolved around so-called newly-weds Speidi - the couple revealed in the final episode on T.V last night that they didn't legally tie the knot last month in Mexico.

Spencer claimed that he wanted to wait before exchanging vows so that Heidi's mother could be present.

We didn't know he was so considerate!

But the couple still insist they are married, even if it hasn't been legally acknowledged.

See them all on the red carpet below