Gareth Anscombe struck a nerveless 80th-minute penalty that gave the Cardiff Blues a 31-30 victory over Gloucester in the Challenge Cup final in Bilbao.

The Blues found themselves with a mountain to climb at half-time at the San Mames Stadium as they trailed 20-6 to a dominant Gloucester.

However, Tomos Williams touched down within a minute of a restart and that try was added to by further scores from Garyn Smith and Blaine Scully before Anscombe's late heroics.

Gloucester will feel they did enough to win the match having scored three tries of their own through Henry Trinder, Mark Atkinson and James Hanson.

Cherry and Whites supporters will also point to key decisions that went against their side. Lewis Ludlow was denied the opportunity to score a try in the first half due to a perceived forward pass from Josh Hohneck, while there was a suspicion that Smith was offside before he touched down for the Blues.

But that should not take away from a fine second-half display from the Blues, who sealed their second Challenge Cup triumph with the biggest second-half fightback in the history of the final to provide head coach Danny Wilson with a fitting send-off as he heads to Wasps.

Cardiff began positively in Bilbao and their intent was rewarded with an early Evans penalty.

However, their luck turned almost immediately as Wales back row Josh Navidi was forced to depart with his arm in a makeshift sling.

By now Gloucester were beginning to build some pressure and they would score the game's opening try with less than nine minutes on the clock.

Jake Polledri, Atkinson, Ruan Ackermann and Ed Slater were all involved in driving the Cherry and Whites into the Blues 22 before Billy Burns hoisted a perfect crossfield kick to the left corner, where Trinder was waiting to score.

Scully was inches from registering an almost immediate reply for the Blues but his foot was just in touch before he grounded the ball.

Evans did cut the deficit with a penalty a couple of minutes later but as the half wore on it was Gloucester who took control.

Twelvetrees restored their four-point lead from the tee before Ludlow was called back by referee Jerome Garces, who deemed Hohneck's brilliant offload had gone forward.

Gloucester would cross the whitewash for a second time before the break, however, thanks to a fine team score that was started by a lovely step from Twelvetrees.

The former England centre beat his man on the outside before finding Callum Braley on his shoulder, with the scrum-half committing the defence before stepping inside and finding the rampaging Atkinson.

It was no less than they deserved and meant the Blues would have to make history if they were to lift the Challenge Cup for a second time.

No team had ever recovered from a 14-point deficit at half-time in a Challenge Cup final but they were given hope within a minute of the restart.

Anscombe did brilliantly to gather his own kick on the right wing before kicking ahead, and after Williams won the foot race to the he displayed fine footballing skills -- and composure after the ball hit the padding on the upright -- to control it and score.

Evans cut the deficit further with a penalty, and then remarkably less than 15 minutes into the second half, Cardiff scored the try that took them into the lead.

Rey Lee-Lo did acted as the battering ram for the Blues and as the ball was recycled Evans dabbed a grubber through that Smith raced onto to score.

Gloucester believed that the replacement was offside, and replays appeared to indicate he may well have been, but Garces was happy to award the try.

The Cherry and Whites did not let their heads drop, however, and within five minutes they had scored their third try as Hanson took advantage of a lineout drive to score from close range.

Twelvetrees converted the try and then added a penalty to stretch the Gloucester lead to seven points with 17 minutes remaining.

It looked as though that would be enough to give them a second Challenge Cup triumph in four seasons, but with under seven minutes left the impressive Ludlow was sin-binned as Gloucester defended on their line.

Within two minutes Scully had slid in to set up a frantic finish that saw Anscombe miss his conversion but make amends with a brilliant last-gasp penalty.