Travolta's rep referred questions about the event to the Church of Scientology. Tommy Davis, the church's spokesman, would not comment on whether the Travoltas or Cruises attended the event. "I would never comment on their behalf," he told ABCNews.com.
Davis did confirm that a celebration of the church's 25th anniversary was held last Friday at the church's property outside London. He said over 6000 Scientologists from around the world attended and that there was nothing "secret" about the event as had been reported previously in the media.
US Weekly reported that the Travoltas and the Cruises reunited at the event.
Travolta and Preston, who have been dealing with their son's death and a related extortion trial, appeared subdued during a performance by a choir, according to one of the magazine's sources.
"John and Kelly were holding hands throughout the performance," an onlooker said. "They look like a very united couple."
Cruise, on the other hand, was "swaying" to the music and "looked like he was in heaven," according to the onlooker. "Katie was next to him doing her best to look as enthusiastic. She was clapping along with the song, but was totally out of sync. Suri was standing by, looking a little bemused in a cute little party dress."
Cruise also addressed the crowd. "Because we never took our eyes off the ultimate prize, we stand where we are today," he said, according to the magazine. "We are in this together!"
Lately, though, it's been the Travoltas standing alone publicly at the extortion trial in the Bahamas. The jury began deliberations this morning to decide the fate of a paramedic and Bahamian lawmaker accused of trying to blackmail Travolta by threatening to say the actor was at fault in his son's death.
Travolta took the stand twice during the trial of paramedic Tarino Lightbourne and Bahamian lawmaker Pleasant Bridgewater.
During his first time on the stand, Travolta detailed his actions on the night of his son's death.
"I ran downstairs with my wife to help my son," Travolta said, according to The Associated Press.
In his testimony, he said he and Preston were awakened by a nanny around 10:15 a.m. Jan. 2, the day of Jett's death. Travolta said that when he went downstairs, another caretaker was doing chest compressions, and he began administering breathing help.
The testimony was apparently the first time Travolta had talked publicly about his son's autism. He had said in the past that Jett suffered from Kawasaki disease, a rare condition in children that involves inflammation of the blood vessels.
Lightbourne rode with Travolta and his son in Jett's last moments.
"It was me, him and Jett," Lightbourne told ABC's "Good Morning America" Jan. 5. "I'll never forget this day. I saw him lean over and hug his son and kiss his son and tell him he loved him and I did everything I could. I saw love in his eyes, I saw love. [Travolta] hugged him, put his arm around him, kissed him on the forehead and the cheek and told him he loved him. He then turned to me and gave me a hug and said, 'You guys did a wonderful job.'"
Both Lightbourne and Bridgewater have pleaded not guilty to conspiracy to commit extortion. If convicted, they could face up to 10 years or more in prison.
ABC News' Mary Rose Abraham and Lee Ferran contributed to this report.