The Grammy award-winning singer garnered a rapturous response for her spine-chilling rendition, not least from Dame Julie Andrews herself, who appeared on stage as a surprise at the end of the performance to hug Gaga and congratulate the artist.

The legendary Oscar-winning star, 79, said she was "especially touched by Lady Gaga’s wonderful performance".

"I have always been a fan, but last night we bonded and now I have a new friend," Andrews said afterwards, in the kind of warm endorsement that is unusual in today's hardened world of critics and competitors.

Appearing on the red carpet earlier on, Gaga revealed that she had invested a lot in the performance. "I really put my heart into preparing it, and I'm really excited to entertain the nominees tonight," she said.

It was unknown what exactly Gaga would be performing at the Academy Awards beforehand, although she let hint with a tweet that read: "Backstage getting ready for my performance! Tonight my heart will be blessed...with the sound of...#Oscars."

Watch Lady Gaga's pitch-perfect Sound of Music tribute at the 2015 Oscars