Harlequins produced a stunning second-half fightback as Danny Orr inspired the London club to a 44-14 Challenge Cup victory over Castleford.

Trailing 14-0 at the break, Quins ran in seven tries after the interval to surge into the fifth round.

In a tough-tackling opening played in driving rain the error count far outweighed any quality football on display.

Both sides had half chances to score, Jon Wells seeing his pass intercepted by Castleford's Andrew Henderson with the line beckoning, and Brent Sherwin's clever kick for the visitors just evaded the chasers.

But, after a scoreless opening 20 minutes, the visitors hit form and punished a subdued home side with a succession of scores.

Anthony Thackeray's grubber kick was fielded by Michael Shenton to plunge over, Craig Huby converting.

Then, after a Huby penalty, quick hands from Stuart Donlan and Kirk Dixon released Adam Fletcher to cross in the corner.

Dixon then added another penalty as Castleford stretched their advantage.

But after the break Harlequins clawed their way back into the game, drawing level within 12 minutes of the restart.

A well-timed Henry Paul pass saw Michael Worrincy weave his way over, and moments later Chad Randall burrowed through after Chris Melling was held.

Rob Purdham converted both and struck a penalty to tie things up.

With the bit firmly between their teeth, Quins took advantage of a tiring Castleford when Tony Clubb then leapt highest to gather Orr's cross kick to give the hosts the lead for the first time.

Orr then got in on the act, weaving past a handful of tackles to score under the posts.

And further late scores from David Howell, Gareth Haggerty and Danny Ward completed the turnaround.