London Irish fly-half Mark Mapletoft slotted 21 points to fire the Exiles into the Powergen Cup semi-finals via a thrilling cup tie on Sunday.

Mapletoft was in inspired form with the boot and landed six of his seven shots at goal, including three monster efforts from around the halfway line.

But it proved a miserable day for his opposite number Glen Jackson, who missed five kicks - including a sitter from in front of the posts which he will want to forget as swiftly as possible.

The hosts took the try-count 2-0, with Matt Cairns and Kris Chesney crossing in each half to keep them in the game.

But it was not enough to end Irish's impressive record at Vicarage Road - this was their fourth consecutive victory at the ground - despite a stirring fightback in the final moments.

A ninth-minute Mapletoft penalty saw Irish draw first blood, ending a promising early spell from Saracens inspired by Thomas Castaignede's clever break in midfield.

Saracens had raced out of the starting blocks. But after their initial flurry it was all Irish, with the visitors' pack clearly holding the edge up front.

Mapletoft slotted another penalty and almost unlocked Saracens' defence with a deft chip over their rapidly advancing back line only to then spill the ball forward when in a threatening position.

The Exiles' lead was extended to nine points on the quarter-hour mark as Mapletoft's boot found its mark once again - although this time the home side managed a reply.

They nearly went over in the right corner, but full-back Mark Bartholomeusz ran out of space before winning a penalty two phases later which Jackson sent between the uprights.

Mapletoft restored the nine-point cushion in the 29th minute after some slick handling swept Irish deep into Saracens territory and drew an infringement from the hosts.

Exiles winger Delon Armitage was hauled down inches short of the line by Bartholomeusz moments later after slipping his way through a cluttered midfield, halting another impressive attack.

But despite Irish's ascendancy, it was Saracens who scored the first try - crossing through Cairns with prominent roles from Kyran Bracken and Bartholomeusz for a beautifully worked score.

Saracens number eight Ben Skirving went tearing through the Exiles' defence shortly after the restart, swatting aside a posse of defenders as he went. But he failed to spot the scoring pass to Tevita Vaikona.

Mapletoft landed two penalties from the halfway line in quick succession to put Irish back in the driving seat - and when Jackson missed his fourth penalty from just wide of the posts it did not look like being Saracens' day.

Just to rub salt into the wound, Mapletoft kicked a monster three points from two metres inside his own half as the home side's indiscipline was ruthlessly punished once again.

Saracens then pounded away at the visitors' line and appeared to have crossed through Bracken only for referee Sean Davey to call back play for a previous infringement.

Eventually the Irish line had to buckle, however, and it finally cracked in the 72nd minute when Vaikona fed substitute Chesney who romped home - with Jackson missing the conversion.

Saracens cranked up the pressure in the dying moments, and the match was there for the taking only for Cairns to spill forward with the line beckoning - allowing Irish to escape into the last four.