Harlequins produced a stunning second half display as they came from 21-8 down to beat Newport Gwent Dragons 31-21 in their LV= Cup clash at the Stoop.
Quins scored tries through Ollie Lindsay-Hague and James Chisholm (two) while debutant fly-half Tim Swiel kicked 16 points in an assured display for his new club.
Jonathan Evans and James Thomas touched down for the Dragons while Dorian Jones kicked 11 points.
Harlequins director of rugby Conor O'Shea named a youthful side containing promising young forwards Charlie Matthews, Kyle Sinckler and Jack Clifford.
Natal Sharks fly-half Swiel, who signed for Quins on-loan until February 2015, was making his home debut for the Londoners who could boast an entire English-qualified matchday squad.
Western Province tighthead Brok Harris, who signed for the Dragons last week, was thrust straight into the starting line-up by Lyn Jones as the Welsh region looked to recover from their 23-6 loss to Ulster in Belfast in the Guiness Pro12 last Friday.
Quins crossed for their first try with only seven minutes on the clock when Lindsay-Hague latched onto a long pass from Swiel to cross in the left corner after sustained pressure from the home pack.
The visitors responded immediately from the kick-off when scrum-half Evans charged down Karl Dickson's attempted box-kick to pounce in the right corner to level matters. Swiel and Jones both missed their conversation attempts to leave the scores tied at 5-5.
Dragons full-back Geraint Rhys Jones missed two penalty efforts but it mattered little as Welsh international flanker Andrew Coombs burst through the Quins defence and offloaded superbly to lock James Thomas to crash over. Jones bisected the posts to make it 12-5.
Swiel fired over a 20th-minute to keep Quins in the hunt but Jones added a further three penalties, including a monster 50 metre effort in the 36th-minute minute, to give his team a commanding 21-8 lead heading into the break.
Quins came firing out of the blocks in the second half and dominated proceedings with Swiel adding another penalty before Dragons hooker Elliot Dee was sent to the sin bin for collapsing a powerful Quins maul.
Number eight Chisholm drove over soon after and Swiel added the extras as a fired-up Quins came roaring back into the contest to make it 18-21.
Swiel knocked over two more three-pointers as O'Shea's side stormed to a 24-21 lead.
Quins went to their driving maul once more with James Chisholm touching down again for the dominant home pack. Swiel made no mistake with the conversion as Quins completed a 31-21 victory.