No 8 Fillier opened his account in the first half and added two more tries after the break as the League 1 East champions elect lifted silverware at the Principality Stadium.
Remarkably, Congreve also crossed for a hat-trick of his own, while Daniel Wall and Thomas Ashmead got their names on the scoreboard too as Brynmawr sealed the first part of what could yet be an historic double.
After a thrilling Bowl final, the Plate clash began in similar fashion with two quick tries for either side. Brynmawr were the first to cross though Congreve, centre Geraint Langdon converting.
Jack Moriarty responded for Conwy – the try was unconverted – before Langdon left the field on a stretcher. Joel Amphlett was his replacement.
It was a big blow to Brynmawr who then fell behind to a neat Conwy try.
No 8 Carwyn Ellis was the scorer, his fellow forwards hooker Ifan Hughes and lock Carwyn Roberts playing vital roles in the build-up with some neat passing.
Arthur Lennon converted from underneath the posts to put the men from North Wales – underdogs for this game – into a 12-7 lead.
Conwy might have been unfancied in the build-up to this one, but things then got even better for them as they crossed for their third try of the day.
Scrum-half Cai Jones was the star man on this occasion, sending Brynmawr’s Congreve the wrong way with a sensational dummy and just making it to the line. Lennon kicked the extras again.
Sensing trouble, Congreve’s acrobatic finish – and unnecessary taunting of a Conwy opponent – got Brynmawr back into it though the try was unconverted.
Langdon’s appearance on the Principality Stadium bench on crutches was a heartening sight and Brynmawr soon gave him further reason to cheer.
After turning down a kickable penalty to opt for a scrum, Ellis’ fellow No 8 Fillier picked up at the back of the set-piece and smashed his way over.
The conversion tied the game at 19-19, but Lennon’s penalty goal after Gavin Knapp was pinged and another Brynmawr try – this time for hooker Wall – meant the Gwent side went to half time with a narrow 24-22 advantage.
Almost immediately after the game resumed Fillier added his second of the day with a tidy finish, burrowing his way through three Conwy tackles to score.
Daniel Butler continued his off day with the boot by hooking the conversion, but Brynmawr were slowly stamping their mark on the game.
The Pirates were dominant up front and their forward superiority showed when another huge scrum surge ended with Fillier crossing for his hat-trick try.
Butler added the extras to what proved to be the game’s crucial score just past the hour mark.
At 36-22 up Brynmawr were always going to have to throw the game away to lose.
And they never looked like doing that, Ashmead crossing for another try almost immediately after in what was a fine length-of-the-field move.
Butler’s extras put the game to bed but Nant Conwy never went away and Caron Davies grabbed a late consolation which Lennon converted.
There was still time for Congreve to complete his hat-trick with another stunning finish and Butler converted from the touchline to bring up the 50-point mark and spark Brynmawr’s celebrations.
