London Irish collected their first LV= Cup win of the season by convincingly defeating the current holders Northampton 37-20 in an entertaining game at the Madejski Stadium.
Irish fielded a much stronger side than Saints, with the home line-up containing around half of their first-choice XV, and the selection paid dividends.
Even allowing for a very slow start, Irish were always the more powerful and penetrative side.
Victory kept alive their remote hopes of qualification for the semi-finals, with Northampton's progress hinging on them defeating Leeds at Franklin's Gardens next week and hoping other results go in their favour.
Northampton had the better of the opening exchanges, with strong running from Bruce Reihana and Greig Tonks enabling the Saints to obtain a position in the home 22.
Joe Ford then missed with a drop-goal attempt and the Irish defence held firm, with a penalty allowing them to relieve the early pressure.
After eight minutes and against the run of play, Irish took the lead when Ryan Lamb kicked a 45-metre penalty.
That lead should have been short-lived for soon afterwards Ford had a good chance to tie up the scores but missed with a 45-metre penalty attempt.
However Saints continued to dominate in territory and possession and their efforts were rewarded when Ford kicked a simple penalty to make it 3-3 at the end of the first quarter.
With 25 minutes gone, Irish managed to construct their first attacking movement of the match.
Wings Sailosi Tagicakibau and Adam Thompstone ran strongly, as did flanker Jamie Gibson, and Irish progressed into the visitors' 22. Saints were penalised and Lamb knocked over the easy kick.
That success spurred the Irish into further action and almost immediately from the restart they produced a flowing movement which brought them the opening try of the match.
Gibson was dragged down narrowly short but hooker Brian Blaney was on hand to drive over for his first try for the club, which Lamb was unable to convert.
Just before the interval Ford kicked a long-range penalty, but with the last movement of the half Irish extended their lead when a long pass from Steffon Armitage sent Blaney over again for the try which Lamb converted with a splendid kick from the touchline to leave Saints 18-6 in arrears at half-time.
Ford had the first opportunity to put points on the board in the second half but his penalty attempt from halfway fell narrowly short.
Irish were then dealt a double blow when Blaney was yellow-carded for deliberate offside and then almost immediately Saints scored their first try when Brett Sharman drove over from close range, with Welsh referee James Jones having to seek confirmation from his touch judge before awarding the try.
Back came Irish and replacement George Stowers drove over for the try which Lamb converted to make it 25-13 to the home side at the end of the third quarter.
Blaney returned from the sin bin and Irish sealed their bonus-point victory when Steffon Armitage powered over from a lineout close to the Saints line.
There was still time for the Irish to produce their best try of the game when Lamb and Elvis Seveali'i combined cleverly to send Daniel Bowden away on an unopposed 20-metre run to the line.
With the last movement of the match Northampton had the final say when Scott Armstrong scored an excellent individual try, beating three men in a 40-metre burst.