All the action from Twickenham.
Full time: Gloucester 40-22 Northampton
80 mins (+6): Gloucester celebrate as they condemn Northampton to their second straight Powergen Cup final defeat.
80 mins (+3): Another pass from Matt Dawson goes astray and Mercier intercepts. He passes to Simpson-Daniel who scores his second try of the match. Mercier converts.
Gloucester 40-22 Northampton
80 mins (+2): The referee will play six minutes of extra time.
80 mins: Thinus Delport is handed what looks like a harsh yellow card for obstruction and will miss the rest of the final.
78 mins: Gloucester concede a needless penalty as Olivier Azam attempts to run the ball out of defence but the Cherry and Whites are soon back in possession and Saints look on their way to defeat.
76 mins: Northampton make a rare sortie into the Gloucester half but another mistake means the attack comes to nothing.
75 mins: Gloucester make a double change with five minutes left, Robert Todd replacing Henry Paul and Junior Paramore coming on for Ed Pearce.
74 mins: Gloucester are desperately unlucky not to score after a slick passing move.
72 mins: The miss does not seem to have dented Mercier's confidence as he takes on another kick from the halfway line - and this time succeeds. Saints now need two converted tries to win.
Gloucester 33-22 Northampton
70 mins: Henry Paul wins a penalty for Gloucester - but Mercier stuns the crowd by missing from just right of the posts.
68 mins: Andy Deacon concedes a penalty in his own half but Saints have the wind against them and the kick barely reaches the halfway line.
65 mins: Gloucester are beginning to take charge as Grayson is penalised for a professional foul on Henry Paul and is shown the yellow card. Mercier scores his fifth goal from six attempts.
Gloucester 30-22 Northampton
55 mins: Northampton bring on Matt Stewart for Robbie Morris.
52 mins: As Northampton seek to ease the pressure, Grayson drops the ball and is penalised for the knock-on. From the resulting scrum, Nick Beal receives a head injury in a collision with team-mate Ben Cohen. Beal plays on after treatment.
43 mins: After a sustained period of defence, Saints cannot stop Jamie Forrester skipping over to put his side back in front. Replays suggest he did not put the ball down cleanly but the referee does not spot the error.
Gloucester 27-22 Northampton
40 mins: More sloppy play from Gloucester as they give the ball away through Mercier. They concede a penalty as Saints threaten a try and Grayson converts.
Gloucester 20-22 Northampton
34 mins: The lead changes hands for the fourth time as Mercier slots over another penalty.
Gloucester 20-19 Northampton
33 mins: Grayson puts his side back in front with a penalty. Gloucester are back to full strength with the return of Fidler.
Gloucester 17-19 Northampton
30 mins: Gloucester make a mockery of their one-man disadvantage as Robbie Morris misses a tackle and 19-year-old Marcel Garvey touches down to become the youngest ever try-scorer in an English cup final. Mercier converts.
Gloucester 17-16 Northampton
25 mins: Gloucester are reeling now as a mistake from Mercier leads to Nick Beal powering over for the try. Grayson converts.
Gloucester 10-16 Northampton
22 mins: Saints' revival continues as Grayson slots home another penalty. Rob Fidler, a late replacement for Mark Cornwell, is sin-binned for killing the ball.
Gloucester 10-9 Northampton
20 mins: Terry Fanuloa is penalised for a deliberate knock-on as he attempts to intercept a pass. Grayson converts the penalty.
Gloucester 10-6 Northampton
17 mins: Northampton have the put-in near the opposition try-line and Paul Grayson skews the ball out of play as his side soak up yet more pressure from the rampant Cherry and Whites.
12 mins: Gloucester move further ahead with a coolly-taken drop goal from Mercier.
Gloucester 10-3 Northampton
7 mins: Northampton's Andrew Blowers is lucky not to be sin-binned for a late charge on Mercier, who cannot convert the resulting penalty.
5 mins: Gloucester gift their rivals a try almost from the kick-off. Matt Dawson's disastrous pass only finds James Simpson-Daniel who gleefully races over. Ludovic Mercier converts.
Gloucester 7-3 Northampton
4 mins: Andy Hazell concedes a penalty in front of the post and Paul Grayson puts Gloucester ahead.
Gloucester 0-3 Northampton
1 min: Gloucester go on the attack immediately with James Simpson-Daniel powering over the halfway line.
1630 BST: The game kicks off.
Gloucester: T Delport; M Garvey, T Fanolua, H Paul, J Simpson-Daniel; L Mercier, A Gomarsall; T Woodman, O Azam, A Deacon, A Eustace, R Fidler, J Boer (capt), A Hazell, J Forrester.
Replacements: C Fortey, R Roncero, E Pearce, J Paramore, C Stuart-Smith, S Amor, R Todd.
Northampton: N Beal; B Reihana, P Jorgensen, J Leslie (co-capt), B Cohen; P Grayson, M Dawson; T Smith, S Thompson, R Morris, M Lord, S Williams, M Connors, B Pountney (co-capt), A Blowers.
Replacements: D Richmond, M Stewart, G Seely, D Fox, J Howard, J Brooks, C Hyndman.
Referee: Tony Spreadbury (RFU).