Peacock has rejected a new contract with the Bulls after nine years at the club and will soon be announced as Leeds' major signing for next season.
"I've had so much success here that it makes it tough to leave,'' said Peacock, who has played exactly 200 games for Bradford. "But I feel that at this stage of my career that I need a new challenge.''
In their quest for replacements, Bradford have been repulsed in a move for Salford's full-back, Carl Fitzpatrick, but have been linked to David Peachey, the Australian who was due to join Widnes before their relegation from Super League was confirmed.
The London Broncos have been told that their half-back and captain, Mark McLinden, will miss the rest of the season after breaking a bone in his leg.
Powergen has confirmed that it is to sponsor the Challenge Cup for another two seasons, with next year's final, hopefully at Wembley, fixed for 26 August.
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