World Series Rugby Sevens protocol states each team must submit their 12-man squad 24 hours before each round begins.
But there is an allowance for replacements to be made if cleared by the tournament doctor.
After a number of false starts, World Rugby eventually confirmed that Hayne would replace Ravouvou, as the Fijian playmaker was officially ruled out by doctors.
Fiji Rugby earlier announced Hayne's inclusion on their Facebook page with an official media release on Friday afternoon, with Hayne's the final name on the list.
"Vodafone Fiji 7s coach, Ben Ryan has named the team that will play in the 10th and Final round of the 2015/16 HSBC World 7s Series in London," the post said.
"The team sees the new inclusion of Jarryd Hayne and the return of Masivesi Dakuwaqa and Viliame Mata."
MEDIA RELEASE - Ryan Names Team for London 7s
Vodafone Fiji 7s coach, Ben Ryan has named the team that will play in the...
Posted by Fiji Rugby on Friday, May 20, 2016
Fiji will play the first of their three pool games against England on Saturday, kicking off at 9:04pm (AEST).
Ryan's squad will also face Wales late on Saturday night, before going head-to-head with Australia in the early hours of Sunday morning.
The final tournament of the HSBC World Series will be Hayne's first and only opportunity to show what he can do during an official Sevens competition, and argue his case for Olympic selection in the No. 1 ranked team in the world.
Once the confusion around Hayne's selection had cleared, World Rugby released exclusive footage of Hayne training with the Fiji squad in their preparations for London.
Fiji only needs to make the quarter-finals in London this weekend to secure back-to-back World Series titles.
They have already won three of the nine World Series rounds to date and also boast two runners-up finishes and two third placings.
Former NRL star Hayne was initially left out of the first 12-man Fiji squad announced on Wednesday, but was still hopeful of a last minute entry as injury cover before registrations with World Rugby closed at 6:30pm on Friday (AEST).
World Rugby had cleared Hayne to play in the London tournament earlier in the week "subject to all other regulatory and registration matters being met", after he declared his intentions to defect to the short-form rugby code.
"He would also be immediately included in World Rugby's pre-Rio 2016 risk-based testing program, which since January 2016 has included a comprehensive program of targeted in and out of competition blood and urine testing on players likely to compete in Rio," the statement said.
Coach Ben Ryan praised Hayne's ability to quickly slot into the squad, noting that he had always intended to use London as an opportunity to try out combinations.
"We always had a plan to mix things up. We got to this point as a team, psychologists talk about this, and we were at a point where I just saw a little bit of halting, we weren't still picking it up. I thought the boys needed a bit of added competition and that came from France, and it has also come from San Francisco," Ryan told World Rugby.
"Jarryd is our latest, he has trained well, (it's a) massive learning curve for him but he has settled in well and he is used to that Fijian side of things off the field when he was with Fiji Bati so that hasn't been an issue at all. He brings a professionalism obviously, and we already have that. We have boys that are at that level where they are self-reliant, self-sufficient and I trust all of them.
"But he comes in from a different angle, he has a great background in rugby league and another professional sport at the highest level. In attack he is comfortable on the ball, he has good spatial awareness and has good footwork. In defence he is a good tackler. It is the shape in defence, the breakdown skills, the finer arts and of course the engine, he is not going to have the same fitness as our boys have got but he's had a good week with us."
Fiji Sevens Squad
Apisai Domolailai, Jasa Veremalua, Waisea Nayacalevu, Isake Katonibau, Viliame Mata, Amenoni Nasilasila, Osea Kolinisau (C), Masivesi Dakuwaqa, Seremaia Tuwai, Kitione Dawai, Samisoni Viriviri, Jarryd Hayne. (As reported by Fiji Rugby)
