Defeat for Albion ensured they cannot claim runners-up spot in Ardal North East.
Bow Street took the points with goals from Iolo ap Dafydd, Tomos Roberts and John James, Callum Mannion and Nic Jones replying for Cefn, who barring a mathematical miracle will end up third.
Caersws completed a double over the Colliers and made sure of a second-place finish, but Chirk already had the league title under lock and key.
The Bluebirds had blown their chances of finishing up champions with a shock 2-0 loss at home to Dolgellau on April 19. Chirk sealed top position by beating Berriew 4-1 last Sunday, April 24.
At the Recreation Ground on Saturday, Luke Mumford and Craig Harris netted for the hosts, substitute Liam Sklenar replying for the table-toppers.
George Finlay and Matthew Worrall put Llay 2-0 up before struggling Brymbo gained reward for a battling display with a 90th minute consolation.
Joe Evans (2) and John Evans shared the goals as Llanuwchllyn stayed fifth with a hard-earned triumph over Y Felinheli.
Iwan Owen scored both for the visitors.
All-square at Alyn Park where both goals came in the first half.
Bradley Knight edged Airbus in front in the 22nd minute, but Lewis Hopwood levelled just past the half-hour.
Mike Kelly and Craig Moore both scored twice and Adam Morris made the scoresheet as Hotspur whipped Porthmadog out of sight, John Littlemore replying for the visitors against his old club.
Sion Thomas and Alex Mayall also found the net for the home side.
Greenfield moved to within two points of the title – although one will probably be enough due to their dominant goal difference – after a 1-1 draw at Cefn Mawr.
In fact, it would all have been decided on Saturday only for Hari Gould netting a 95th minute equaliser for Rangers.
Dean Hyland had edged Greenfield in front in the 56th minute.
A Ricky Evans penalty and Seb Kidd strike banked the points for Lex, Ben Wilson responding with a spot-kick for Llangollen.
David Jones (penalty), Luke Williams and Dewi Nicholson put Caerwys 3-0 up inside six minutes.
Williams was dismissed for a second yellow on 64 minutes, after which Kacper Wojciech managed a 77th minute response for the Lawmen.
Although Stuart Williams missed an early penalty for the visitors they went on to dish out a thrashing at Tower Field.
The floodgates did not open until the second half, Luca Nardo breaking the deadlock on 51 minutes.
Williams made up for the penalty miss with a five-minute hat-trick and he later added a fourth, Thomas Eyes and Allister Belk also on the mark for the away side.
Liam Prytherch delivered a double for the Spartans in this home win.
Jay Wiles, Michael Fleetwood and Harvey Hammersley added singles, Jacob Williams and Keanu Bruton hitting back for Coedy.
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