Matthew Taylor struck twice as Old Illtydians upset champions Garndiffaith 24-22 in Division Four East on Saturday. Taylor went under the posts with five minutes remaining to set up an easy conversion for former Wales international Matthew Back.
Back, at fly half, scored a try, penalty and three conversions in total as Old Illtydians finish the season level on points with the Garn but lose out on the title on tries scored.
Elsewhere on the final day in Division Four East, Llandaff gave their home supporters something to cheer about with an 18-15 defeat of Machen and Tredegar Ironsides won 24-31 at Llandaff North.
Llantwit Fardre finished fourth from bottom thanks to a 27-12 defeat of Mountain Ash in Division Two East.
In Division Three East champions Penallta capped a fine season with a typically high-scoring performance as they hammered basement dwellers Abercarn 7-92.
Third placed St Peters scored 12 tries in their 74-10 demolition of visiting Hirwaun in Division Three South East while runners up Llanishen scored 27 without reply at home to Brecon.
Second from bottom Cefn Coed finished in sixth after they edged out third from bottom Porth Quins 8-10 in the final game of the season in Division Four South East.
In Division Five East second placed Gwernyfed hammered third from bottom Oakdale 55-7.
Tonmawr failed to shake off their Division Two title celebrations from midweek after they were held to a draw at Maesteg Quins.
Victory over Seven Sisters took Tonmawr ahead of Corus at the top of the table but the champions, only beaten once all season, took their foot off the gas to be held 7-7 by Quins.
Llangefni stole second place in Division Three after edging out Ammanford 12-5 to move ahead of Aberystwyth in the final table. Lampeter completed a good day for North Wales winning 34-24 against Pembroke Dock Quins, completing a disappointing season for the West Walians.
Mumbles gave Mike Ruddock the perfect send off before the former Wales Coach takes over at Guinness Premiership outfit Worcester Warriors with an emphatic 73-0 victory at Cwmgors.
Aberavon Quins secured fourth place with a 25-3 win over Skewen while bottom side Brynamman were denied the chance to give their supporters some late cheer, going down 26-22 at home to Nantyfyllon.
BP Llandarcy drew level on points at the top of Division Four south-west with Briton Ferry with a 36-13 win at Trebanos. Third-placed Glynneath ran riot, winning 80-29 at Taibach. Penygroes went down to a rare defeat in Division Five, 11-3 at Cefneithen. Crynant finished third in Division Five after edging a 31-30 thriller at Cwmgwrach.