For so long a fortress, it was Northampton's third defeat at Franklin's Gardens in the league, and it was down to some magnificent Gloucester defence as Saints were twice stopped on the line and held up over it once, with the back row duo of Sione Kalamafoni and Akapusi Qera superb.
May conjured a piece of magic in the first half and then pounced on a dropped ball for a 70 metre try for his second. After that it was dogged defence from Gloucester who took revenge for losing at home to Northampton at the start of the season.
Wasps' deadly wing duo Tom Varndell and Christian Wade both struck to sink leaders Harlequins 17-16 as Nick Evans missed the chance to pinch victory for the champions at the death.
Varndell and Wade both scored first half tries and while Quins romped back, Evans missed a 78th-minute penalty which would have almost certainly won it for his side and extended their winning run to 11 matches.
Tom Hooper scored the only try for the home side with Evans booting the rest of their points while Nick Robinson kicked seven points for Wasps.
Leicester continued their relentless charge towards a play-off place with a 28-12 win against London Welsh thanks largely to the goal-kicking of departing fly-half George Ford.
Publicly criticised for his decision to depart Welford Road this summer, Ford produced a near-faultless display in the absence of England international Toby Flood with 13 points.
Adam Thompstone scored a first-half try, with Niall Morris and Dan Bowden touching down for the Tigers after the break, while Gordon Ross scored 12 points for the Exiles.
A fluent attacking performance from Bath earned them a welcome 32-9 bonus-point victory against Worcester.
It was not quite enough to overtake seventh-placed Exeter - the two west country sides are now level on points - but it was Bath's fifth win in succession in all competitions, suggesting they are building momentum for an assault on several fronts.
First-half tries from Peter Stringer and hooker Rob Webber gave Bath a 13-9 lead, and they went on to dominate the second half with further tries by wings Tom Biggs and Horacio Agulla (two).
Worcester's only points were three first-half penalties from Danny Gray.
London Irish secured a crucial 29-16 victory over Saracens at the Madejski Stadium in their battle for survival.
With a win for fellow strugglers Sale on Friday night, there was great pressure on Irish but they responded magnificently to overcome second-placed Sarries at the Madejski Stadium.
It was 9-9 at the break after Tom Homer and Charlie Hodgson both landed three penalties, but a crucial interception try from Shane Geraghty put the Irish on the road to victory. Ofisa Treviranus also crossed, while Homer's overall contribution was 19 points.
David Strettle scored a try in the second period for the visitors, with Hodgson adding the extras.