Golden Globe nominee Sam Smith and host Ricky Gervais were some of the first stars to arrive on the red carpet at the glamorous awards ceremony.
The singer, who is nominated for best original song for his single Writing's On The Wall from the James Bond film Spectre, opted for a classic black tuxedo, while Gervais added a pair of mirrored sunglasses.
Arriving with his girlfriend Jane Fallon, Gervais joked: "I'm heavily sedated under doctor's orders."
Speaking to E!'s Ryan Seacrest, the comedian said his hosting rehearsal featured a string of jokes that he will not be able to tell in the packed ballroom.
He said: "I did it just for fun to get it out of my system. I don't know when I can ever use those jokes."
Gervais added: "Every time I do something like this I'm looking forward to it being over so I can have a little reward, I'm not cut out for this."
Asked by Seacrest if Gervais has a drink before such events, Fallon replied: "Before, during, after."
Gervais is returning to the hosting job for a fourth time but is a controversial choice because of his cutting jokes about the famous faces in attendance.
Actresses Bryce Dallas Howard, Jaimie Alexander and Gina Rodriguez added a touch of glamour to the red carpet proceedings in dramatic gowns.
Rodriguez, who opted for a navy blue Zac Posen gown, is nominated for the best TV comedy actress award for her title role in Jane The Virgin after winning for the same part last year and was joined on the red carpet by her father.
Alexander, who was dressed in a plunging emerald gown by Italian designer Genny, was accompanied by her fiancee Peter Facinelli.