hi its not very long about 17mm - and its been over tightened !!!! no other reason - lets take into account it doesn't hold the tensioner on lol its just a bolt which the tensioner rotates around - so its not a tensioner problem -
you will find the bolt section should just turn out - as its not a tightened bolt like i said - use a reverse drill bit or a nice branded punch the tuen it out no need to drill - i have some drill bits from snap on which would be perfect to snag it and turn it out
regards
Steve