A last-minute try by the Glasgow captain, Alastair Kellock, rather spoiled Saracens' afternoon after they had threatened to run away with this Pool Four match at Vicarage Road.
Kellock's try, in the fifth minute of added time, rewarded his side for their hard work and earned a losing bonus point. That could prove significant when these two meet again in Scotland in the final pool match, in the New Year.
The Scots at times matched Saracens with their willingness to run the ball from anywhere. They defended soundly and attacked with precision, revealing some deft touches. They were the more consistent of the two teams.
When Saracens were good they were very polished, the hooker Matt Cairns, scrum-half and captain Neil de Kock and England centre Andy Farrell catching the eye. There was panache and derring-do, which was great to watch. But when they were bad, notably in defence, their discipline fell off and they looked poor.
Fortunately for them, they did enough to keep Glasgow at bay and they too picked up a bonus point, for scoring four tries.
This is a dangerous Glasgow side, as their opening try illustrated. It was scored by the open-side flanker, John Barclay, and it began with a slippery piece of counter-attacking by the Argentinian full-back, Bernardo Stortoni. He must have covered a pitch and a half in his mazy progress from deep in the Glasgow half, after Glen Jackson had missed touch from a penalty.
When Stortoni ran out of steam Barclay was on hand for a free run-in. Unfortunately for Glasgow, though, Saracens had already scored twice, the first following a powerful break by the right wing, Rodd Penney. As he ran into Glasgow defenders Penney swivelled and found Cairns, who presented the lock Hugh Vyvyan with a scoring pass. The second try came midway through the first half, Jackson looping around and finger-tipping the ball to Penney.
A mighty shove at a five-metre scrum then culminated in the No 8, Ben Skirving, plunging over in added time.
There had been two penalties apiece for Jackson and Glasgow's Dan Parks and the English side were comfortably ahead at the interval.
Carelessness, however, saw Saracens concede two penalties early in the second half. From one of them, 52m out, Parks narrowed the gap.
It needed a brilliantly worked set-play off an attacking scrum, resulting in the wing Kameli Ratuvou crossing for his third try in two games, to restore home fortunes. Jackson's third penalty then got them far enough ahead for victory, but Hefin O'Hare's 76th-minute try, which Parks converted, was a great prelude to Kellock's grand finish.
It gets no easier. Saracens face a daunting trip to Biarritz at the weekend. They can afford even fewer errors down there.
Saracens: Tries Vyvyan, Penney, Skirving, Ratuvou; Conversions Jackson 2; Penalties Jackson 3.
Glasgow: Tries Barclay, O'Hare, Kellock; Conversions Parks 2; Penalties Parks 4.
Saracens: F Leonelli (E Thrower, 64); R Penney, K Sorrell, A Farrell, K Ratuvou; G Jackson (G Ross, 40), N de Kock (capt; M Rauluni, 40); K Yates (T Mercey, 40), M Cairns (F Ongaro, 40), C Johnson, H Vyvyan, K Chesney (T Ryder, 70), P Gustard, R Hill (D Seymour, 69), B Skirving.
Glasgow: B Stortoni (S Barrow, 3-8); L Fa'atau, A Henderson (Barrow, 54), D Gibson, T Evans (H O'Hare, 19); D Parks, C O'Young (S Pinder, 57); J Va'a (E Kalman, 57), F Thomson (E Milligan, 70), M Low, A Newman (D Turner, ht), A Kellock (capt), K Brown, J Barclay (J Eddie, 70), J Beattie.
Referee: R Poite (France).Reuse content