Scarlets enjoyed Pro14 revenge against Leinster on Saturday, winning a rematch of last season’s final.
The Welsh province lost their crown to Leinster in a thrilling contest in Dublin last May, but they were back on top with a 23-21 victory.
Gareth Davies put the game beyond Leinster, with Rhys Ruddock’s try five minutes from time not enough to rescue a result.
Allan scored the first try of the match, but Treviso gifted the visitors a penalty try before they touched down again through Braam Steyn.
Although Cardiff’s only other points came with the boot, Gareth Anscombe’s trio of second-half penalties looked to be enough for victory until Monty Ioane dramatically crossed and Allan delivered.
Josh Lewis inspired the Dragons to a 27-22 defeat of Southern Kings, scoring a crucial 17 points, while Connacht eased to a 32-13 win over Zebre.
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