Cardiff Blues made it three wins from three in the PRO12 after they edged out fellow pace-setters Glasgow 23-19 at the Arms Park on Friday.
Someone's 100 percent record had to give as these two met for the first time this season.
Both sides had their dominant periods in the first-half. Alex Cuthbert scored to get Cardiff Blues off to a good start but Glasgow hit back with tries of their own from Stuart Hogg and Peter Horne.
Reynold Lee-Lo scored in the last play of the first-half to hand the lead back to Cardiff Blues at 20-14, two Gareth Anscombe penalties the only difference between the two sides.
Ali Price got the first and only try of the second-half, a late Steve Shingler penalty eventually sealing Glasgow's fate as the home side went on to win 23-19.
The Scotsmen had not been defeated by a Welsh region since Scarlets visited Scotstoun in round 1 last season and had won their last ten fixtures against Blues in the PRO12.
Anscombe opened the scoring with two successful penalty attempts in the opening quarter.
After successive waves of Blues pressure Cuthbert eventually managed to sneak his way through for the game's first try. Anscombe added the extras to give the home side a 13-0 lead.
Glasgow hit back immediately slicing through Cardiff for a beautifully worked Hogg try. Clegg scored the conversion to help get the Warriors back in the game at 13-7.
Horne got on the score sheet for Glasgow as the game's momentum completely shifted. Clegg bagged the conversion to put the visitors in front for the first time in the match.
An offload from Josh Navidi found Lee-Lo for a phenomenal last gasp try to put Cardiff ahead on the stroke of half-time. Anscombe got the conversion to make it 20-14 going into the break.
Glasgow got first blood of the second-half with a try from Price but Clegg shanked the conversion to keep Glasgow behind by one point.
A late Shingler penalty sealed the victory for Cardiff Blues.
For Cardiff Blues:
Tries: Cuthbert, Lee-Lo
Cons: Anscombe 2
Pens: Anscombe 2, Shingler
Tries: Hogg, Horne, Price
Cons: Clegg 2
Cardiff Blues: 15 Matthew Morgan, 14 Alex Cuthbert, 13 Cory Allen, 12 Rey Lee-Lo, 11 Tom James, 10 Gareth Anscombe, 9 Lloyd Williams, 8 Josh Navidi, 7 Ellis Jenkins, 6 Sam Warburton, 5 Josh Turnbull, 4 George Earle, 3 Taufa'ao Filise, 2 Kristian Dacey, 1 Gethin Jenkins
Replacements: 16 Matthew Rees, 17 Rhys Gill, 18 Scott Andrews, 19 Macauley Cook, 20 Nick Williams, 21 Tomos Williams, 22 Steven Shingler, 23 Blaine Scully
Glasgow Warriors: 15 Stuart Hogg, 14 Tommy Seymour, 13 Nick Grigg, 12 Peter Horne, 11 Lee Jones, 10 Rory Clegg, 9 Ali Price, 8 Josh Strauss, 7 Ryan Wilson, 6 Rob Harley, 5 Jonny Gray (c), 4 Tim Swinson, 3 Zander Fagerson, 2 Fraser Brown, 1 Gordon Reid
Replacements: 16 Pat MacArthur, 17 Alex Allan, 18 Sila Puafisi, 19 Greg Peterson, 20 Lewis Wynne, 21 Grayson Hart, 22 Mark Bennett, 23 Rory Hughes
Referee: George Clancy (Ireland)
Assistant Referees: Gary Conway (Ireland), Simon Rees (Wales)