Sileby Rangers moved six points clear of the UCL Premier Division relegation zone as unpredictable Desborough suffered a surprise 3-2 home reverse.
Mark Redding put Ar Tarn in front after 10 minutes.
Stuart McMichael equalised two minutes past the half hour and a 43rd-minute Aaron King goal had the visitors in front at the interval.
John Dean added Sileby’s third goal after 64 minutes.
Michael Byrne’s 19th goal of the season, an 80th-minute spot kick, closed the gap but Ar Tarn were unable to find a leveller.
In division one, ON Chenecks avenged an early season home loss to Lutterworth Athletic with a 2-0 win at Hall Park.
Ben Lewington broke the deadlock two minutes past the hour and the Chenecks win was wrapped up five minutes later when George Clarke scored from the penalty spot.
Bugbrooke took the points in their home fixture against Olney for the sixth time in seven seasons, winning 4-1.
Brad Janes put the home side in front after ten minutes.
Sam O’Neill equalised for the Nurserymen after 26 minutes.
The home lead was restored by Jamie Inwood seven minutes before the interval.
Janes added a home third three minutes into the second period.
The home success was sealed by Matt Johnson two minutes from time.
Woodford United picked up their first win in five outings with a 4-2 success at Blackstones.
Joe Henderson’s seventh-minute Reds opener was matched within a minute by a Kieran Arthur reply for Stones.
Arthur gave the home side the lead after 32 minutes.
Adam Creaney put Woodford level after 48 minutes.
On the hour Creaney gave Woodford the lead for a second time and their victory was sealed by Ben Foster after 73 minutes.