Rushden & Higham have thrown the Midlands Three East (South) title race wide open by inflicting a first defeat of the season on Stamford.
The leaders had gone into the game at Manor Park with a record of 12 wins from 12 - including a 17-12 success in the reverse fixture earlier this campaign.
But Rushden - who continue their pursuit of the Senior Vase this coming weekend - were in merciless form and ran out convincing 31-11 winners.
Stewarts & Lloyds took advantage of the result and kept their promotion hopes alive with a 50-0 home victory over Deepings.
Both Kettering and Wellingborough lost their respective games, the Blues going down 35-20 at Old Northamptonians while Boro lost out 22-15 at home to Lutterworth.
The relegation-threatened Cut Throat Lane side were 15-0 down inside the opening quarter as they made life very hard for themselves.
Tries for Pete Vickers and Luke Gardiner dragged them back level but, with the visiting pack in control, Lutterworth managed to score again to seal the win.
Oundle got the better of Corby in the Midlands Four East (South) clash.
It took them just four minutes to get off the mark as Toby Snelling finished off a break.
Simon New stretched the lead as he was involved twice in one of their best tries of the season before Dan Burns powered and then Snelling intercepted to bring more joy for Oundle.
After the break Richard Griffiths bagged himself two scores with Chris Woodford and Stephen Cull also getting their names on the scoresheet as the 48-0 win was completed.
Oundle coach Peter Croot said: “We scored eight tries and got the vital bonus point.
“We have a way to go, though, to challenge for promotion. We must improve execution.”
Corby manager Ricky Egan added: “When the game started I thought this was going to be lambs to the slaughter.
“We are getting too worked up and making silly mistakes.
“At half-time I told the guys to calm down and from them on we started to look a match for Oundle.
“I have no complaints with this defeat. It was a good game played fairly and the best team won.”
Old Grammarians had another rough afternoon as they were beaten 74-10 at home by St Neots.
Sharnbrook & Colworth lost out 47-17 in a fiercely-contested friendly against Old Scouts.
Gary Mitchell and Ed Strand got their tries with Mitchell and Cameron Bennett converting. Strand added a penalty.