The Broncos started the match in dominant fashion as they went 16-0 up after only ten minutes.
Matt Cook survived two tackles before passing to Michael Robertson, who scored the first try after only three minutes.
Cook then extended the lead just minutes later as he powered over the line following good work from Michael Witt.
Witt added two goals in the opening stages before Michael Channing scored his side's third try of the match on ten minutes.
Bradford forced their way back into the match on 18 minutes as Karl Pryce collected Luke Gale's kick to touch down.
Platt scored his first try of the match to reduce the deficit to just one but Witt continued to frustrate the visitors by this time adding a try of his own to extend the hosts' lead.
Platt proved to be a thorne in the side of the Broncos' defence and his sheer strength ensured that he scored his second try of the match in the corner.
Bradford looked to be in full flow at the start of the second period and were rewarded for their quality as Platt evaded a number of tackles to complete his hat-trick of tries.
The away side took the lead on 62 minutes when Platt scored his fourth following a flowing move from the Bradford backs.
Gale put the match beyond doubt as he added a penalty with ten minutes left before converting a last-minute drop goal.