The Broncos were without Greg Fleming, John Timu and Shane Millard, who were all still feeling the effects of last week's defeat against Leeds. But they still managed to storm into an 18-8 half-time lead against the Saints despite going eight points behind inside the first 10 minutes.
But the tide soon changed midway through the first half when a neatly weighted cross-field kick from Hammond found Tollett, who collected the ball in mid-air before going over the try-line.
New-signing Glen Air and Scott Cram then crashed over to give the Broncos a ten-point interval advantage.
The Saints rallied but, after Joynt had touched down, Warton kicked the Broncos six points ahead. But back came the Saints and Long went over for a converted try which left the teams level at 20-points each with less than 20 minutes left.
But with just four minutes remaining, Great Britain centre Paul Newlove accepted what looked a forward pass to go over for the match-winning try and gave Saints their ninth successive victory.
The Broncos are away for the next two Super League games against Halifax and Huddersfield/Sheffield, and then the club is taking its "home" game against Warrington to Newport, in Wales, as part of the Super League's annual European roadshow exhibition.
Broncos are not back at The Valley until the evening of Sunday, June 11, when they are hoping for a Super League crowd attendance record against Castleford Tigers.
The Tigers have already confirmed they will bee bringing at least 6,000 supporters. Call 020 8853 8800 for ticket details.
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