HUDDERSFIELD Giants were again left counting the cost of a slack second half display as they became the first side to lose in the capital this season.
Former Giant Chris Thorman inspired the Broncos to their first win on home soil in 10 months with a try and six goals as his side turned on the style with three scores in the final 20 minutes.
Until then, the Giants were in with a shout of pulling off another win against much-fancied opposition, largely thanks to the try-scoring efforts of Brandon Costin.
Costin took his total for the season to 18 with a brace (one in each half) to extend his record of scoring in seven successive games - and his second try after 51 minutes meant that he had scored his side's last six tries.
Thorman, who helped the Giants bounce back into Super League at the first attempt, was more than his equal, however, as his ex-teammates struggled to find a way of containing him.
Thorman may not have had his own way quite as often had Stanley Gene not been ruled out with a shoulder injury, but coach Tony Smith was given a pre-match boost when Paul Reilly and Jamie Bloem passed fitness tests.
The Giants started badly and gave away an early penalty for a swinging arm, which gave the Broncos the opportunity to kick the ball deep into their territory.
Thorman was able to combine with halfback partner Rob Purdham to send in Dennis Moran, who rounded his man at speed before touching down and Thorman added the goal.
Former Bronco Iain Morrison was lucky not to have been sent off for a sixth-minute trip on Moran, which was clearly seen by everyone in the ground except for referee Bob Connelly and his two touch judges.
Less than a minute later Moran knocked on just metres from the line from a scrum awarded after Giants winger Marcus St Hilaire spilled the ball trying to get back into the field of play from behind his own line.
But just as it looked as if the slow-starting Giants were going to get overrun, they managed to pull themselves back into the game after 13 minutes through Costin.
Broncos second row Steele Retchless knocked on inside his own 20, and Bloem and the impressive Ben Roarty worked an opening for Costin to cross from close range.
The opening period was littered with handling errors by both sides while the Giants frequently gave away penalties in key positions.
Broncos didn't have it all their own way, however, with Moran needing to produce a desperate ankle tap to deny Paul March from scoring a certain try after more good work from Roarty.
March then kicked through and Moran again cleaned up, but took a knee in the thigh, which was to put him out of the game as the Giants enjoyed their best period.
They had three successive sets of six, twice forcing the Broncos to drop out under their own sticks, only to see Costin knock-on after March and Julian Bailey had set him up.
The Giants then had a let off four minutes before the interval, whenLondon won a scrum against the head, only for Thorman to knock-on five metres out after doing all the hard work.
The Geordie also missed a chance to give Broncos a 39th minute lead when Huddersfield were penalised for pulling back Tony Martin as he hunted down a kick through.
But less than a minute later a head high tackle gave him another chance from straight in front of the posts to take the two points on offer.
The Giants started the second half brightly and Costin tried to use Hefin O'Hare's pace to good effect with a clever kick, but Jim Dymock read the danger and got back to clear up.
The Broncos ended up working the ball down the pitch and Thorman opted to go down the short side before handing on to Nigel Roy, who passed on his inside to Retchless to crash over.
In years gone by that would have signalled the end of the Giants, but that is not the style of the team who have recently beaten Leeds and Wigan and they hit back as they did in the first half.
Mick Sicker turned provider for Costin who, from a standing start, threw a body swerve to send the defence the wrong way and Steve McNamara's second goal reduced the home side's lead to just two points.
But instead of it being game on, Thorman just moved into overdrive and Andrew King plucked his high kick out of the night sky to touch down after Retchless had made good yards.
Thorman, who started for Yorkshire in the Origin game, crossed the line himself after being set up by Dymock and he rubbed further salt into the wounds with the goal.
He did have a drop goal attempt blocked, before King intercepted Costin's pass to race home untouched for his second try of the evening nine minutes from time for his second brace of the season against the Giants.
St Hilaire pulled off a try-saving tackle on Martin after former Bradford Bull Paul Sykes made a dangerous run down the right flank as the Broncos piled on the pressure.
The Giants had some consolation in the dying seconds of the game as Costin kicked down the right wing, and with no cover on hand O'Hare used his pace to collect the ball and touch down.
But it was too late, the damage having already been done.
The Giants missed out on the chance to move level with Widnes and closer to Warrington Wolves, having now played the same number of games, 19, as their rivals.
Giants: Reilly, O'Hare, Costin, Bailey, St Hilaire, March, Holroyd, Fleary, McNamara, Gannon, Morrison, Roarty, Bloem; Cooper, Whittaker, Slicker, Grayshon
BEN ROARTY narrowly edged out Brandon Costin for his sheer workload in the first half in particular when his side found it tough in getting going.
JIM DYMOCK'S tackle on Hefin O'Hare that stopped a certain try. Moments later the Broncos were able to extend their lead to eight points, meaning the Giants needed two tries to hit back.
Broncos: Moran, King, Martin, Roy, Sykes, Purdham, Thorman, Marshall, Budworth, Stephenson, Retchless, Peden, Dymock; Bawden, Kennedy, Gallagher, Jackson.
Broncos tries: Moran 2 mins, Retchless 45 mins, King 60 and 71 mins, Thorman 65 mins. Goals: Thorman 6/7.
Giants tries: Costin 15 and 52 mins, O'Hare 79 mins. Goals: McNamara 2/3.
Half Time: Broncos 8 Giants 6
Referee: Bob Connolly (Warrington)