The following circumstance relates to the current year's audit of Alpha Limited:

Alpha Limited has a large manufacturing centre in Sydney which produces concrete and pipes to be used in its projects. The company policy is to include the land and buildings in the Balance Sheet at market value less accumulated depreciation. The factory is included in the Balance Sheet based on a valuation carried out five years ago. Based on your understanding of the Sydney property market, you believe that there is likely to have been a significant increase in the market value of land and buildings and that, in accordance with Australian Accounting Standards, the land and buildings should be reported at the materially higher current market value.

Alpha Limited agrees to hire a valuer to determine the current market value of the land and buildings and agrees to increase the carrying amount of the land and buildings to reflect the higher amount determined by the valuer. Note that the company hired the valuer, and the auditor agrees with the valuation.

Required Is the auditor's use of the work of the valuation expert appropriate, and what effect would these circumstances have on the auditor's opinion?