Given the heavy rain throughout the afternoon that had made the Vicarage Road pitch thoroughly sodden it was no surprise that high kicks were the order of the day. But the first 40 minutes proved to be an entertaining half of rugby, starting with a Peter Stringer blindside break and kick ahead that had Martin Roberts scrambling back, albeit comfortably.
Saints' initial approach was pretty direct, a powerful maul forcing the home forwards to come offside and concede a penalty. Stephen Myler, whose first shot at goal had dropped just right of the uprights, made no mistake and the three points that this yielded were certainly deserved.
But Saracens hit back almost immediately through Charlie Hodgson, and with their next attack also forcing the visitors into diving into a breakdown the England man pushed his team into the lead.
Having conceded that second penalty Saints put together their best set of attacking phases of the match so far. Soane Tonga'uiha made yards through the middle, Myler asked questions of the fringe defence and George Pisi rounded his man to put Scott Armstrong away down the left wing.
The defence was there to cover, but Saints had shown that they were in town to play some rugby. That said, the mauling remained an effective weapon, too, and with Saracens unable to clear their lines another powerful effort brought another penalty. It was in a similar position to Myler's first attempt, and it similarly drifted off target.
The conditions may have been heavy but the skill level on show from both teams was admirably high. James Short sidestepped three defenders to start a dangerous run ended only by a great Calum Clark tackle and Vasily Artemyev took an outstanding catch under severe pressure.
But with things so tight a bit of luck goes a long way, no more so when a Myler drop-out bounced over Andy Saull and into touch just outside the home 22. Stringer launched a box kick that went straight up in the air, and with a number of Saracens offside a penalty was forthcoming, as was another three points from Myler's right boot.
It was no more than the Saints deserved, but when the ball was fumbled a couple of phases after the re-start Saracens had a great position. Saints held out the initial charges, and as the hosts' attacks ground ever slower a shot at goal looked increasingly likely.
Saints came over the top at a ruck, up stepped Hodgson and the action took its 15-minute break with the hosts leading 9-6.
The second half started poorly from the Saints' perspective, Hodgson landing a further two penalties in the space of three minutes to put clear space between the teams for the first time.
Myler replied in kind to keep Saints in touch going into the final quarter, but while the weather was worsening Hodgson's goal kicking remained on song and his sixth success took the margin back out to nine points.
Saints may have edged the first half, but they were failing to fire in the second. The play was certainly being played at Saracens' pace, with the visitors finding it hard to regain the momentum they had shown in patches before the break.
The second half was summed up in the space of 90 seconds. A Myler chip was read easily by the defence, while when Schalk Brits' speculative pass between his legs hit the deck it found a team mate not an opponent.
So going into the final five minutes Saints were seeking a bonus point, not the win. But as Saracens' defence kept on pressing and forcing the visitors back from halfway to inside their own 22, even the single point looked a long way off.
But one final effort got Saints within kicking range, and although Lamb saw his first attempt drop agonizingly underneath the crossbar his second shot two minutes later was flighted perfectly into the wind and drifted inside the right-hand upright to earn his team the reward they deserved.
REFEREE David ROSE
6mins SAINTS Miss pen Myler
10mins SAINTS Pen Myler 0-3
12mins SAR Pen Hodgson 3-3
16mins SAT Pen Hodgson 6-3
21mins SAINTS Miss pen Myler
36mins SAINTS Pen Myler 6-6
40mins SAR Pen Hodgson 9-6
HALF-TIME SARACENS 9 SAINTS 6
49mins SAR Pen Hodgson 12-6
52mins SAR Pen Hodgson 15-6
54mins SAINTS Pen Myler 15-9
63mins SAR Pen Hodgson 18-9
77mins SAINTS Miss pen Lamb
79mins SAINTS Pen Lamb 18-12
FULL-TIME SARACENS 18 SAINTS 12