Tredegar Ironsides were the team of the day in the Swalec Plate, claiming a terrific 31-8 win away at Rhymney, despite sitting a league below in Division Four East.
Jonathan Mills scored two of the away sides four tries and Ryan Hall claimed 11 points from the boot to seal a memorable win.
Risca of Division Four East put in a terrific performance to stun Croesyceiliog of Division Three East 20-15 away from home, while the students of Cardiff University pulled off another upset, beating Fairwater 17-14.
Rhydyfelin were the big scorers of the day, running home six tries on their way to a 41-0 demolition of Cilfyndd.
Mike Huckeridge claimed a try as Treherbert of Division Two East overcame a late scare to edge out Brecon 14-12, and
Tonyrefail came out in top of the all-Division Four East clash, beating Pentyrch 27-17 in a thrilling contest.
Elsewhere Mountain Ash beat Nelson 26-6, and Blaina claimed an impressive away win as they beat Division Three East rivals Abertillery Blaenau Gwent 20-8.
Abercarn pulled off the shock of the round in the Swalec Bowl, the Division Five East side beat Abergavenny of Division Two East 21-17.
Tries from Nicky Lloyd and Matthew Johnson had put Abercarn 13-12 ahead at half-time before Jack Davies put the home side 20-12 ahead. A late try from Abergavenny set up a tense finish, but the home side bravely held on to ensure a famous win.
John Mayler scored two tries as Old Penarthians gained an impressive 20-0 victory away at Canton and Ross Howells also claimed a brace as Ferndale beat Rhigos 20-8, Luke Rees claimed the other try for the Bulldogs.
Dowlais were the big scorers of the day as they ran in six tries to beat St Albans 45-3.
Crumlin put in a great performance away from home to beat Cefn Coed 34-0, while Usk also won away from home, they beat Llanhilleth 10-17.
Rhiwbina won 19-14 away at Cardiff HSOB, and Pontyclun also claimed a narrow win, beating Bridgend Sports 15-9. In the remaining game in the Swalec Bowl, Abervan failed to field a side against Newtown.
Nearly 40 players were involved in the first Wales Under 18 training session of the season. WRU National Performance Manager Gethin Watts is excited at the potential shown by the group and expects the Regional Under 18 Championship to hone their skills even further.