Markham captured the cup and completed the treble over their opponents having won both their Division Six meetings earlier this season, but Beaufort competed strongly in this final at Tredegar RFC.
The favourites swept into an early lead with wing Anthony John landing two penalty goals and after 11 minutes their outstanding centre Gareth Price paved the way for a try in the corner by co-centre Lewis Hughes.
Markham extended their lead when Price weaved his way over from a movement begun by fullback Rob Landregan, but Beaufort got on the board when fly half Matthew Jordan placed a penalty.
Beaufort stepped up their efforts in the second half as referee Darren Jones allowed the game to flow and wing Scott Griffiths put over a penalty that was soon cancelled out by one from Anthony John.
After 55 minutes strong play by No.8 Jason Coombes and centre Mike Vaughan took Beaufort close and finally centre Mike White did well to score as he was tackled.
At 19-11 Markham came back with Shaun Trollope and skipper Scott Mullins at the head of rushes that led to Gareth Price sending his younger brother Gavin over for the final score. Another brother and former Markham player is current Neath hooker Gerwyn Price.
Markham: R Landregan; A John, L Hughes, Gareth Price, Gavin Price; D Carpenter, S Morgan; D Sinnet, D Rixon, M Rose, I Coonik, C Hall, S Trollope, S Mullins (Capt), C Morgan
Beaufort: D Roper; S Griffiths, M Vaughan, M White, K Purnell; M Jordan, D Smith; J Roberts, G Moon, J Phillips (Capt), D Casey, M Easley, J Taylor, J Coombes, J Bennett
Referee: Darren Jones (WRU)