The problems initially occurred following the discovery of damage to the tower. Work was then carried out to remove the affected stone.
But this week the further removal of two of the tower’s bells by stonemasons uncovered the core of the problems; a rusted iron hoop in the middle of the stonework at the level of the cracked arches.
Alan Paul, Senior Manager explained: "A wrought iron hoop had been built into the middle of the wall, just behind the apex of the lancet arches. This was probably used to reinforce the tower, in order to prevent the walls spreading due to the weight of the spire.
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"It is very badly corroded and when iron and steel corrode they expand. This expansion results in significant force on the stone, pushing it out, causing it to crack and also forcing the joints open.
"The hoop is located immediately behind the worst areas of damage to the stone and has expanded significantly, so we are certain that this is the cause. The rest of the affected sections of stone will now be removed.
"The remaining two bells will also be taken out using a block and tackle so there should be no further need to use the crane and traffic control, unless we come across some particularly large blocks of stone."
When the dismantling work has been carried out, a temporary roof will be put in place to weatherproof the tower.
The tower will then be put back together using as much of the original stone as possible.
In addition, the clock mechanism has been removed to keep it safe during the works.
(IT/GK)
