As champagne flowed, courtesy of an open bar tab, the 23-year-old tennis ace then hit the stage with a rousing performance, including Cold Chisel's hit Khe Sanh, as his devoted new fiancee looked on.
At the celebrations were Hewitt's parents, Cherilyn and Glynn, his sister Jaslyn and her boyfriend, Swedish tennis ace Joachim Johansson
, Adelaide Crows star Andrew McLeod, Channel 7 presenter Bruce McAvaney, and Davis Cup coaches Wally Masur and John Fitzgerald.
One source described the four-carat diamond ring, bought at Tiffany's in Collins St, as a "boulder".
"It's awesome. I am really happy," Cartwright said yesterday, after flying to Sydney to resume filming Home and Away.
One party insider said Hewitt rose to the occasion with flying colours.
"It was a wonderful night . . . a very intimate affair where Lleyton really demonstrated what a mature young man he has grown into," the source said. "He made a great speech, mostly about tennis, where he thanked all his family and friends.
"Roger Rasheed actually announced the engagement, but everyone had their suspicions after seeing the rock on Bec's finger when they entered the room. It was huge and it had light bouncing off it all over the place."
The party continued until about 3am, when Hewitt headed to Crown casino with Cartwright and a handful of friends.
The couple got together at Richard Branson's Virgin party in December. They met five years ago at a Starlight Foundation dinner.
Both broke up with their partners in the final months of last year.In October, Hewitt split from Kim Clijsters after a four-year relationship. They had planned to marry this week.
Hewitt's camp sought Cartwright's phone number after she broke up with actor Beau Brady.
(WTF!? Some sources say they've known each other for years, and now... after he breaks up with Kim, he's looking for Bec's number!? I don't mind, I mean, Bec is
and Lleyton is fine off the court
but this sentence
is so weird!)
The engagement yesterday dominated talkback radio and Internet fan forums around the world, with mixed opinions being aired. Some praised Hewitt for his romantic haste; others said he was naive and on the rebound.
Sources said Hewitt's family was fully behind the engagement.
Cartwright is contracted for the year on Home and Away, so she will have little time to travel the international tennis circuit.
After that, she could become a regular, the source said.