Not all assets depreciate in value; some appreciate in value, Buy to let properties and Commercial Real Estate for example.
If you have an asset that generates income, a shop for example, an amount is allocated for the amount of income earned, and classed as Good will; this would then be added to the asset worth, the total of which is the sale price.
Occasionally, the amount of Good will is over stated at the time of the sale, and the purchaser ends up declaring an impairment further down the line - I think it is called amortisation.
If the Ground was valued at 41m in the latest accounts, a figure you would have to conclude was correct, how do you suddenly get to 80m on asset value alone, less than 12 months later?
Some other factor must have been included in the sale price and my guess is rental income; if that is correct, the expected income must be at the higher end of the scale.