Azarulllah is brought into the attack for the fourth over of the innings. Davies picks up four with a fine glance and Maxwell follows up with back-to-back sixes (the 33rd and 34th of the day!). The first was smashed over long-off after Maxwell gave himself a bit of room and the second was a short ball helped over square-leg.
Willey just got enough seam movement to evade Roy's drive although it wasn't the best shot, no foot movement. Australian Glenn Maxwell is the new batsman for Surrey and he can give it a tap. Not yet though, just a single from his first four deliveries.
Roy is bowled driving at a delivery that came back off the seam from left-arm seamer Willey.
Steven Crook, the batting hero of Northants' semi-final win, wasn't requried to bat but will open the bowling with his medium pace. Roy has started well, finding the boundary at midwicket and then running well for a couple of twos. Eight-an-over is not going to get it done for Surrey though.
Roy hits the fielder with one well-timed drive and then takes a couple of steps down to drive through the covers for Surrey's opening boundary. Willey also donates a wide to the cause.
Willey opened the batting in some style for Northants and now is going to open the bowling with his left-arm seam. Jason Roy and Davies are the Surrey openers.
Because the rain break came so early in Northants' innings there is no revision on the Duckworth-Lewis method. Surrey need 195 from 18 overs to win the Friends Life t20 title.
Mahmood is going to finish things off for Surrey. White gets in a tangle going for big heave but the resulting edge falls safely on the off side for a couple of runs. Surrey's miserable night continues as a no-ball is called because they only had three inside the circle (Northants obviously have that effect on opposition captains as Essex did the same in the semi-final). Mahmood follows up with a bouncer that is called wide. A hard-run two brings up the century stand from 56 balls and leaves White needing two off the final delivery for his half-century... White dispatches a short ball for six to finish on 54 not out.
Dernbach's first three overs disappeared for 44 runs but he will continue to finish his allocation. Wakely completes a 25-ball half-century with a bottom-edged cut for four from the opening delivery. Dernbach tries to get in a couple of yorkers outside off-stump in but is called wide on each occasion by umpire Michael Gough. Dernbach is not happy, shaking his head. Dernbach finishes with 0-55, narrowly avoiding the worst bowling figures in finals day history.
Wonderful shot from White, giving himself a bit of room and driving for six back over Mahmood's head. Mahmood responds with some shorter stuff but it doesn't really work as White and Wakely scamper through for a total of 12 runs from the over.
Dernbach is having a nightmare. He came off second best after having words with Willey earlier and now Wakely is tucking into some loose offerings. Wakely gets four behind square on the leg side and, later in the over, picks Dernbach's slower ball and smashes it for six to midwicket.
Wicketkeeper Steven Davies is up at the stumps to De Bruyn's medium pace as Surrey continue their spinner embargo (apart from the first over from Ansari which cost just one run). Wakely pulls a short ball behind square for four, bit of a freebie. Four more for Wakely, this time steered behind square on the off side to bring up the 50-partnership with White from 31 balls.
Dernbach's first over cost 21 and his second over doesn't start too well either, Wakely dumping the second ball for six with a short-arm pull. Dernbach responds well with a few of his slower ball variations.
Wakely drives over for mid-off for four. Northants have certainly had their share of luck in this innings already, a thin edge from Wakely off De Bruyn's bowling races away for another four between the wicketkeeper and short third-man.
White has taken a while to get going - conditions are not that easy for batting despite the way Willey made it look - but he is now into his stride with a couple of late cuts off Lewis, the second of which goes fine for four.
The ball has been changed by the umpires because it had become too damp.
Another of Surrey's medium pacers, Zander de Bruyn, is into the attack. Wakely opens his account with an outside edge to third-man for four. Good ball but it still disappeared.
Northants skipper Alex Wakely joins White in the middle after Willey's exit. The game is set up for Northants, can they push on?
Lewis gets the breakthough as Willey holes out to Gary Wilson at deep midwicket. Willey's 27-ball contribution featured six fours and four sixes.
Tremlett continues into his third over. White gets an outside edge down to the third-man fence for his first boundary. Willey drives just to the leg-side of straight for another four, this has been a superb exhibition of clean striking from the left-hander.
Jon Lewis into the attack. Willey, only opening because Coetzer is injured, clears mid-off for six to complete a 19-ball half-century, the quickest in the competition this year. Willey gets away with a top-edged heave that falls safely behind square on the leg side. Time for a spinner?
Tremlett fails to pick up a return drive from Willey. It was straight at him at chest height but he didn't see it until too late.
Willey doesn't appear too bothered by the delay. He blocks Dernbach's first ball but then goes back into all-out attack mode - six, four, four, four, two.
Game reduced to 18 overs per side, Jade Dernbach into the attack for the resumption.
The groundstaff have started the clearing up process and a 7.50pm (BST) restart is now on the cards.
The radar suggests it should clear up in around 20 minutes. Fingers crossed. There is a reserve day tomorrow - although it would be a new 20-over game if that was the case.
Rain getting heavier now, the full covers are being put back on. Frustrating.
The hovercover is still in place. All the other covers have been taken off.
Bad news - the drizzle has returned and the umpires are out in the middle with their brollies up. That 7.25pm restart is looking unlikely.
Some interesting dance moves in the crowd during this delay to say the least!
It will be tough for the bowlers for the rest of this game with a wet ball.
The rain has stopped and the groundstaff are busy removing the covers. We'll be good to go again in about 10 minutes.
We are in for a bit of a delay. The rain is coming down hard and the covers are in place. There is half-an-hour's grace before we start losing overs.
An eventful over from Mahmood ends with the players being taken off the field as the rain starts to come down more heavily. Willey dispatched the first four balls for 15 runs - including a one-bounce four over mid-off and two leg-side sixes - before Levi was bowled. New batsman Cameron White plays out a dot ball to end the over but by now the rain is coming down hard.
After being hit for 15 off his first four deliveries of the over, Mahmood responds by uprooting Levi's off-stump. The South African was aiming across the line.
Willey greets the introduction of Tremlett with a lofted drive over cover for four. Tremlett didn't think much of that and responds with a short ball that rears up and Willey does well to fend for a single. Wow! Levi pulls a short ball off the front foot for a huge six over midwicket.
The umpires are happy to stick it out for the moment. If the rain gets much heavier they'll have to go off though. Chris Tremlett replaces Ansari after just a solitary over for the spinner.
Azhar Mahmood's first ball is pushed through the covers for four by Levi. Sweet piece of timing. Drizzle in the air at the moment, the ball is skidding through. Quick drop-and-run to mid-off brings Willey onto strike and he opens his account with a single chopped down to third-man from the final ball.
Inside edge saves Levi from being lbw to the second ball of the match. The burly South African is soon off the mark with a single worked to midwicket. Good first over for Surrey, just one run from it, ends with the left-handed Willey playing and missing outside off-stump.
Left-arm spinner Zafar Ansari is going to bowl the first over. David Willey has been promoted to open alongside Richard Levi for Northants in Coetzer's place.
The players shake hands on the outfield before Surrey go into a huddle for some last-minute words of inspiration from skipper Vikram Solanki. Here we go...
Surrey are unchanged from the side that beat Hampshire an hour or so ago, while Northants have brought in England Under 19 skipper Ben Duckett for Kyle Coetzer, who has a wrist problem.
Surrey won the toss and chose to bowl first.
Welcome to our coverage of the Friends Life t20 final between Northants and Surrey. Play starts at 6.45pm (BST).