The weight of the ancient cannon has flattened out its wood and metal wheels
Mons Meg, the historic cannon on the ramparts of Edinburgh Castle is to undergo a service after officials found the great gun had a flat wheel.
The pressure of the six-ton barrel and the two-ton carriage has distorted the metal band round one of the wheels.
Historic Scotland experts had to call in two cranes to lift the barrel for investigations to be carried out.
The conservation work and a paint job is expected to take between a week and ten days to complete.
Hugh Morrison of Historic Scotland said: "This was the supergun of its era and it's one of a kind, so we take very good care of her with regular checks and maintenance.
"As she is so large we are having to set up special lifting gear to hoist her off the carriage.
"But once that's done we'll be able to check her over and carry out any conservation work that's needed, and put on some new protective paint as required.
"One job that has to be done is to knock a metal rim on one of the wheels back into shape as it has bent out of shape from the enormous weight of the gun."
Mons Meg was originally made in 1449 and presented to James II in 1457, at which time she was the latest in military technology, and fired gunstones weighing 330lbs or 150kg.
When fired in 1558, to celebrate the marriage of Mary, Queen of Scots to the French dauphin, Francois, the gunstone reached Wardie Muir, nearly two miles away.
The gun was last fired in October 1681 in a birthday salute for the Duke of Albany (later James VII) but her barrel burst.