Rees stood pitchside as the players left the pitch and told the crowd of their gratitude to everyone who turned up.
He said: “I want to thank you all on behalf of the players and the coaches for turning up today. We have really enjoyed having you here and I hope you all agree this has been a great success.”
The fans were admitted free of charge to the training session which was a genuine training run and part of the RBS 6 Nations schedule for the squad.
The crowd was made up of thousands of children and players stayed behind after the run out to sign scores of autographs.
The team also threw signed small size rugby balls into the crowd to show their appreciation to the supporters who turned up.
The day included pre session entertainment with pitchside interviews, a kicking competition for young fans and a chance to watch Shane Williams pass rugby balls through a larger than life model of the former England hooker Brian Moore’s mouth.
The session was the second open training session for fans to watch following a successful launch of the project last Autumn when some 3,000 fans turned up at the Millennium Stadium.
The Six Nations session included a warm up, rugby skills, tackling and kicking as the full squad took part.
At one stage the coaches encouraged the fans to make as much noise as possible as James Hook, Stephen Jones and Rhys Priestland practiced place kicks.
The session was compered by Phil Steele of BBC Wales who was joined by the former Scarlet, Wales and British and Irish Lions player Scott Quinnell to describe the on field action.
It was one of the squads final training sessions in Wales before they head for Italy later this week to play Italy in Rome on Saturday.
