Tonbridge Juddians have missed out on their fourth straight promotion, losing 19-8 to Chinnor in the National Two South play-off.
TJ's were undone by exemplary kicking from Chinnor fly-half James Catchcart in a windy contest at Kingsey Road.
Coach James Simpson told BBC Radio Kent: "This was just one game too far for us this season.
"To go up three seasons on the trot and get through to the play-offs, we need to be proud of our achievement there."
Cathcart kicked 14 points for the Oxfordshire side, with Mark Chase adding a solitary try.
In reply Tonbridge could only muster a single penalty from Charlie Harding and a try from John Tabrett.
Simpson admitted that there were lessons to be learned if they wish to challenge for top honours again next season, adding: "We need to make sure we maintain some strength in our forwards.
"We were beaten by Chinnor in our forwards and the loose play and the scrummage, where we were out-muscled.
"The game against Ampthill last week was a physically demanding game and I think this game was similar and just a little bit too much for some of them.
"We tried to bandage them up and hold them together but it was just not going to happen."
Chinnor join already promoted Canterbury in the National Two South next season, but not Westcombe Park.
Despite winning four of their final six matches of the season, including a final day 27-16 victory over Southend, Lydney's win over Barnes sealed Combe's fate.
They will be joined in the National Three South-East and London by TJs, Gravesend and Old Elthamians, who defeated Colchester 16-8 in the play-offs.
Kent premier club Blackheath completed an unprecedented 11th consecutive league win, triumphing 24-10 over Rosslyn Park.
Captain Tom Bason told BBC Radio Kent: "We've really hit our straps and kept going.
"We haven't changed an awful amount. Once we won a couple of games, we've been unstoppable.
"It's great and we've played some really good stuff along the way."