Celtic managed to hold off the stern challenge of Hearts and wrap up the SPL championship thanks to John Hartson's early strike.
The big striker celebrated his 31st birthday with a sweetly struck volley from distance after just three minutes.
The title race is over with six games left to play but it was far from an easy ride for Gordon Strachan's side.
Celtic goalkeeper Artur Boruc had to make fine saves to twice deny Roman Bednar and then Rudi Skacel.
It was a nervous night for the home support as their nearest rivals Hearts more than matched them in a bruising contest.
The visitors looked more comfortable on the ball and were quick to close Celtic down.
But Celtic ground out the victory with some tenacious tackling of their own and a sound display from Boruc and his defenders.
It looked as if Celtic might run away with it when Hartson got the party off to a flying start with a wonderful volley.
Maciej Zurawski nodded a long punt down field from Boruc to the Welshman, who caught the ball 25 yards out and watched it bounce once before grazing the fingertips of Craig Gordon on its way into the net.
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The visiting goalkeeper was caught out by Hartson's opportunism and his positioning was not what it could have been before the strike.
Hearts responded well and almost snatched a goal back immediately.
Bednar spun cleverly inside the penalty area and sent a low shot towards the bottom corner but Boruc threw himself to his left to tip the ball behind.
Tynecastle defender Andy Webster gave Boruc a scare with a long-range lob onto the top of the net after Stephen McManus had failed to clear his lines properly.
Celtic were struggling to build on their promising opening and Gordon comfortably saved Shunsuke Nakamura's 30-yard free-kick as the first-half came to a close.
Hearts thought they had levelled the game five minutes after the break when Webster bundled the ball home from close range, but the Scotland international had strayed offside.
Celtic defender Bobo Balde mis-hit a shot straight at Gordon from a good position before Boruc was at full-stretch to keep out a low, angled strike from Bednar.
The Polish keeper then had to make a similar stop to keep out an effort from Hearts substitute Skacel.
Hearts were claiming for a penalty when Balde mis-timed a clearance and whacked the striker, with interim manager Valdas Ivanauskas sent to the stands for his protest.
The final few minutes saw Hearts camped in and around the Celtic penalty area, but Celtic held firm to secure a league and League Cup double in Strachan's first season at the club.
Celtic: Boruc, Telfer, Balde, McManus, Wilson, Nakamura (Pearson 58), Petrov, Lennon, Maloney (McGeady 82), Zurawski, Hartson (Dublin 69). Subs Not Used: Marshall, Thompson, Varga, Wallace.
Booked: Hartson, Telfer. Goal: Hartson 4.
Hearts: Gordon, Neilson, Webster, Berra, Fyssas, Cesnauskis, Hartley, Brellier (Elliot 85), Mikoliunas (Skacel 62), Bednar, Jankauskas (Pospisil 54). Subs Not Used: Banks, Tall, Aguiar, Petras.
Booked: Fyssas, Brellier, Elliot.
Att: 59,699
Ref: D McDonald