Burns' response was superb though and he took the fight to Martinez, playing the hard-hitting champion at his own game and landing a string of powerful shots throughout a gripping 12 rounds.
Martinez, who won the title from Essex fighter Nicky Cook in Manchester inside four rounds last March, had twice defended his title convincingly and won 15 of his 25 previous fights within the distance.
The clear favourite must have thought he was on his way to another simple success when his right hand had Burns down for a mandatory eight count towards the end of the first round, although Burns seemed to have been pushed off balance more than badly shaken.
Burns landed some powerful shots in the following round but Martinez was able to duck out of harm's way and had Burns on the ropes in the closing seconds. An uppercut rocked the champion in the following round but he recovered and a powerful right jab had Burns falling back on the ropes in the final seconds.
The fourth round continued in the same manner with both boxers landing powerful punches, although the champion's mobility appeared to be an advantage.
I showed heart of a champion - Burns
But Burns took the fifth round convincingly, two brilliant right hooks putting Martinez under serious pressure at either end, the Coatbridge boxer producing an impressive sequence of punches after the first and the bell then coming to Martinez's rescue.
Commonwealth champion Burns dominated the next three rounds although Martinez never looked completely out of the contest. The ninth round was a scrappier affair but Burns finished it in trouble after finding himself on the ropes and struggling to get back on the front foot.
The Scot recovered well in an even 10th round and gained the upper hand in the penultimate round despite being caught by a left hook in the final seconds.
Martinez came out with all guns blazing in the final round but Burns, roared on by an electric crowd, found the most damaging punch of the round and remained in control despite the champion catching him with a low blow, which was punished by the referee.
"Throughout the fight he did catch us a few times," Burns told Sky Sports. "But, as I said before, I do have a good chin and I took them well. I had to grit my teeth every round there and I'm just overwhelmed.
"I couldn't ask for a better camp behind me, the build up to this fight all I could think about was winning this world title, and now it's here I don't know what to say."
The fight had everything - Warren
In the chief support, Simpson was taking part in his 12th title fight and his experience looked to have told in the middle stages but the 27-year-old tired visibly towards the end of the 12 rounds.
After 116-114 verdicts either way, judge Ian John Lewis awarded the 24-year-old the contest by four rounds to hand him the belt and a guaranteed shot at Martin Lindsay's British title.
The opening two rounds appeared to go either way but Smith's right eye was cut in the third after an apparent clash of heads and Simpson landed two accurate jabs that made their mark in the following round.
Smith was using his jab to good effect but he was caught by sporadic right hooks, although he hurt Simpson in the final stages of the sixth round with a body shot.
An ill-tempered fight remained tight in every sense and more bad feeling was apparent when Simpson retaliated after being caught by his opponent after the bell had signalled the end of the seventh round.
The fight opened up slightly in the ninth and Simpson recovered from an early blow to land several decent shots.
But Smith, whose older brother Paul is British super-middleweight champion, looked more in control in the closing stages, adding several powerful strikes to his consistent jabs to take the belt.
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