Northampton and Leeds entertained a sell-out crowd at Franklin's Gardens with a ten-try scoring feast as the hosts ran out 38-24 winners.
But despite their bonus-point win, cup holders Northampton exited the LV=Cup while Leeds finished the tournament without a win and only two points.
Despite having nothing to play for, the visitors gave one of their best performances of the season in the first half and at one stage led the strongest available Saints side by 19-7, but the home pack dominated proceedings after the interval to ensure a deserved victory.
After 10 minutes Leeds took the lead with a try of real quality. They moved the ball slickly through numerous phases and following crucial incursions from Hendre Fourie and Lachlan Mackay, James Tincknell outflanked the home defence to score the try which Ceiron Thomas was unable to convert.
Five minutes later Leeds went further ahead, Brett Sharman losing possession in his own 22 allowing the visitors to swiftly counter-attack with a movement which ended with Fourie driving over for the score.
Thomas converted to give Leeds a 12-0 lead at the end of the first quarter.
The Saints at last showed some urgency and from a line-out in the Leeds 22, Shane Geraghty ran strongly for a solo try which he converted, but that success was soon nullified when Fourie again ran powerfully into the heart of the home defence to set up a position from which James Craig crossed for the try which Thomas converted.
Leeds were then dealt a big blow when hooker Phil Nilsen was yellow carded and Saints took immediate advantage when Sharman forced his way over from a lineout.
Leeds made a half-time change replacing the impressive Fourie with club captain Marco Wentzel, but the flanker was missed as the Saints upped their game to level the scores after 50 when Roger Wilson went over under the posts for Bruce Reihana to convert.
Northampton took the lead for the first time in the match after 57 minutes when Ryan Powell dummied over to secure a bonus point.
The home side then made a host of substitutions to give their young players a chance, but they continued to maintain sustained pressure and this was rewarded with further tries from replacement scrum-half, Stuart Commins and Greig Tonks with one further conversion from Reihana.
With the last movement of the match, replacement Jacob Rowan scored a consolation try for the visitors to earn them a deserved bonus point.