The Group’s policy is to write off the difference
between the cost of each item of property,
plant and equipment and its residual value over
its estimated useful life on a straight-line basis.
Assets under construction are not depreciated.
Reviews are made annually of the estimated
remaining lives and residual values of
individual productive assets, taking account of
commercial and technological obsolescence
as well as normal wear and tear. Under this
policy it becomes impractical to calculate
average asset lives exactly. However, the total
lives range from approximately 10 to 50 years
for buildings, and three to 15 years for plant
and equipment. All items of property, plant and
equipment are tested for impairment when
there are indications that the carrying value
may not be recoverable. Any impairment
losses are recognised immediately in profit.