AceShowbiz - Julia Roberts was "regretfully unable" to present her pal George Clooney with the AFI Lifetime Achievement Award on Thursday, June 07 after an unexpected change in her filming schedule.

The actress had initially been announced as one of the main guests invited to pay tribute to her frequent co-star at the annual gala, which is hosted by officials from the American Film Institute, but Julia had to pull out at late notice.

An AFI spokesperson explained the Pretty Woman icon was disappointed to be missing the event, adding to E! News, "Ms. Roberts is currently in production and due to a change in schedule, it was not possible to participate as planned".

It's not clear what project Julia was working on, but she wasn't a complete no-show - she featured in a pre-recorded video message feting her Ocean's Eleven leading man Clooney.

Jennifer Aniston, Don Cheadle, Anna Kendrick, Richard Kind, Juliana Margulies, Bill Murray, and comedian Jimmy Kimmel were also on hand to applaud Clooney's career at the Dolby Theatre celebration, where his wife, Amal Clooney, gave attendees a rare insight into their private lives, gushing about the Kentucky-born "gentleman" who showed her real love does exist after resigning herself to "the idea that I was going to be a spinster".

"He is the person who has my complete admiration and also the person whose smile makes me melt every time," she shared. "My love, what I have found with you is the great love I always hoped existed. And seeing you with our children, Ella and Alexander, is the greatest joy in my life".

And as George stepped up to accept the prestigious honour from Hollywood veteran Shirley MacLaine, he expressed his gratitude to "everyone who came out tonight to say such beautiful things... and Jimmy Kimmel!".

"I love every rotten one of you," he smiled.