London's full time status was the telling factor in their 29-10 victory over the Sheffield Eagles to end the hosts' 12 month unbeaten streak at the Don Valley Stadium.
The contrasting game plans of both sides were clear throughout the match. London attempted to make the most of their size advantage to pound the part time Eagles into submission.
The hosts, meanwhile, attempted to win the contest through a willingness to move the ball that has made them one of the nation's most exciting teams to watch.
The latter's approach bore sizable fruit in the early exchanges, but as the game progressed, it was clear that the superior physical attributes of the Broncos pack, led by boom forwards such as Antonio Kaufusi and ably guided by the magnificent Jamie Soward at stand-off, enabled them to force errors from the hosts and eventually gain a tight grip on the contest.
London began with a bang, providing an early sign of the physical assault they would unleash on the hosts as immediately from the kick off, Kaufusi forced Eagles scrum half Dominic Brambani to knock on with a big hit.
However, Broncos prop Tony Clubb was unable to take advantage from the resulting set of six, knocking on a short ball with the line begging.
The rest of the first quarter, however, belonged to Sheffield. The Eagles were demonstrating all the flair that has led them to second place in the Championship this season, with sleek offloading play from inside their own half almost resulting in a try for Scott Turner, while an excellent 40-20 from Brambani on the third tackle provided an indication of the creative approach that was most likely to reap the rewards for the hosts.
The full time - part time fitness gap began to show in the second quarter, however, as London forced several errors in the tackle from the Eagles, leading to the opening try from Michael Witt on 21 minutes, as he fended off the covering Pat Walker to score near the posts, converting his own try.
Despite an unconverted Sheffield reply four minutes later from Scott Turner, who gathered a Menzie Yere flick pass to score in the left corner, London were easily the dominant side, finding an increasing number of gaps in the tiring Eagles defence.
It was, however, a superb individual effort, rather than one of attrition, that put the Broncos ahead two minutes later; as Soward's lateral run cast doubts in the minds of the defence, allowing him to get on the outside of Tom Armstrong to score in the left corner from 50 metres out, with Witt's missed conversion making the scoreline 10-4, which stayed in place for the rest of the half.
Sheffield did not divert from their game plan, however, continuing to move the ball for the rest of the match. A memorable length of field break from Misi Taulapapa almost resulted in a try in the 38th minute, while Turner was bundled into touch on 43 minutes after good work from the men inside him.
London extended their lead with a controversial try on 46 minutes, as Tom Armstrong's fumble of a high kick was grounded by Michael Robertson; video ref Ben Thaler discounting a possible knock on from Dan Sarginson and the fact that Michael Robertson appeared to be in an offside position. Nonetheless, Witt's conversion extended London's lead to 12 points.
Flashes of brilliance from both sides were evident for the rest of the third quarter, but it was London who made their lead even greater on 59 minutes.The build up to the try followed a familiar pattern; an unforced error in the guise of a penalty conceded from offside, and tiring defence as Shane Rodney glided through some porous tackling to touch down next to the posts, with Soward converting this time to give London a 22-6 lead.
Soward's drop goal on 62 minutes extended the lead further as London began to close out the game, making their physicality count. The Broncos began to make more metres with every tackle, with a further tries from debutant Rhodri Lloyd on 65 minutes after a Kaufusi offload, converted by Soward, demonstrating their ability to find gaps in a defence that was unused to the intensity provided by Super League opposition
The Eagles never gave up, pulling a try back through the dangerous Yere three minutes later, converted by Walker, with an excellent kick and chase, with Tom Armstrong leading the charge, perfectly summarising their fighting spirit.
In the end, however, it was London's ability to cope better with the intensity that a Challenge Cup fixture always provides that saw them run out worthy winners, but Sheffield's willingness to move the ball, in conjunction with their relentless determination, always gave them a chance, adding an exciting edge to the match that made it a compelling affair for the neutral spectator.
Sheffield: Laulu Togagae, Taulapapa, Yere, Armstrong, Turner, Walker,
Brambani, Battye, Henderson, Stringer (c), Garside, Straugheir, Hirst
Replacements: Green, Davey, Szostak, Roche
T: Turner, Yere
London: Dorn, O'Callaghan, Lloyd, Sarginson, Robertson, Soward, Witt, Kaufusi, Lee, Clubb, Rodney, McMeeken, Krasniqi.
Replacements: Bryant, Fisher, Wheeldon, Melling.
T: Witt, Soward, Robertson, Rodney, Lloyd
G: Witt (2), Soward (2).
Man of the match: Jamie Soward