Indeed it was as a result of some debris 300m from touchdown of 27R. 2 aircraft on final approach were told about it by the tower and elected to continue approach and land safely, a Korean 747 decided to go around. This was then followed by a Midland (I think) F100, then we started switching to 27L.
Single runway operations give 6 mile gaps to the tower so that will be why you had to hold for so long - the average delay on the screen was showing as 62 minutes. When the runway reopened, Tower allowed TEAM operations whereby landing 27L and 27R to clear the backlog. All was back to normal again by around 1830 local.