London Irish survived a spell with just 12 men to hand Saracens their first Premiership defeat of the campaign in an absorbing contest.

Jackson landed five penalties to punish an indisciplined Sarries and converted both scores as Irish held out.

Scrappy Sarries crossed through Kapeli Pifeleti and Sean Maitland.

Exiles captain Adam Coleman went in the opening 40 when his shoulder connected with hooker Tom Woolstencroft's head, while Saracens back-rower Ben Earl's failure to wrap and contact with the head saw him also depart in a first half lasting about an hour.

Woolstencroft was forced off after the heavy blow but after the match director of rugby McCall said he was "up and about".

Despite being beaten, Sarries stay 10 points clear at the top as second-placed Sale were beaten at Newcastle.

Having been narrowly edged out in defeats by Leicester, Exeter, Harlequins and Gloucester by less than five points, Declan Kidney will have been delighted to see Irish come out on the right side of the scoreboard.

This was just their third win of the season, and was the product of huge heart and resolve to knock off the league leaders and deny them a losing-bonus point of their own.

Not only did they have the red card of Coleman, but sin-bins for Rory Jennings and Rob Simmons within minutes of each other during the second half saw them go down to 12 - and they also overcame the loss of Will Joseph to injury, which left them a back short for much of the game.

They dominated the set-piece, harrying the visitors' line-out and forcing a slew of free-kicks at the scrum, with fly-half Jackson buzzing on the back of their supremacy with incisive carries.

Hassell-Collins' bump and spin finish out wide was the result of sharp hands on the back of field position created by a teasing kick from Ben Loader, while Tom Pearson's rampaging run late on set the platform for Cunningham-South to power over.

Yet it was the defensive mindset, in the face of some relentless attack, that helped the hosts over the line, and frustrated a Saracens side who had won their first nine Premiership games of the season.

Although this was their first league game since November, Mark McCall's Sarries had passed their European examinations against Edinburgh and Lyon in recent weeks.

At Brentford though, the set-piece issues hurt them, while the stellar back division of Elliot Daly, Owen Farrell and Alex Goode were unable to deliver enough of a threat when the numerical advantage was with them.

Pifeleti ground his way over after an Exiles penalty gifted field position just before the break, while Daly's grubber was messed up by Lucio Sinti for Maitland's score.

In the end though, despite getting within a score's reach, Irish kept them at arm's length for a priceless victory.

London Irish director of rugby Declan Kidney told BBC Radio London:

"It was some game to watch, lots of ebbs and flows, what happened there has actually surprised me. We've been knocking on the door, but we got a bit of reward tonight. You can look at a few pivotal points in a match and there were a lot of them tonight which is what made it so entertaining.

"The lads are such a pleasure to work with. Tonight we got them held up over the line, got a goalline drop out, and gave up an attacking position. But it's those little things do make a big difference.

"You have to learn how to win, Saracens know how to win. We're learning how to win, and we showed a lot of our learnings tonight. One swallow doesn't make a summer, but I'm just delighted for everyone in the organisation because there's been a bit of adversity. The collective effort of everybody was fantastic."

Saracens director of rugby Mark McCall told BBC Radio London:

"Hats off to London Irish, they were by far the better team and deserved their win.

"We seemed off it from the get-go, never played with the energy and clear minds that we normally do. We seemed rattled and distracted.

"We were on their goalline, they were down to 12 men and you've got to find a way to score in that situation - for whatever reason we didn't."

London Irish: Loader; Cinti, Joseph, van Rensburg, Hassell-Collins; Jackson, White; Goodrick-Clarke, Willemse, Hoskins, Ratuniyarawa, Coleman (capt), Gonzalez, Pearson, Fa'aso'o.

Replacements: Ruiz, Fischetti, Parker, Munga, Simmons, Cunningham-South, Englefield, Jennings.

Sin-bin: Jennings (60), Simmons (61)

Red card: Coleman (15)

Saracens: Goode; Lewington, Daly, Tompkins, Maitland; Farrell (capt), Van Zyl; M Vunipola, Woolstencroft, Riccioni, Isiekwe, Tizard, Christie, Earl, B Vunipola

Replacements: Pifeleti, Hislop, Bello, Kitchener, Wray, Davies, Howlett, Malins

Red card: Earl (29)

Referee: Matthew Carley