The depreciation is predicted by experts who may be right or may be wrong. Book retail for the car you describe is £18,400. If you can get it for £17,000 it will have already depreciated by more than £13,000 in its first year. So if it's going to depreciate by 80 per cent by the end of its third year it will be worth £6000 in two years time, which means that after paying £17,000 you stand to lose £11,000.

At auction on Friday a 61,000 mile 2009 Volvo S80 2.4D 175SE manual sold for £7950. The original list price was about £26,000, so over three years and 60,000 miles that implies a residual percentage of 31 per cent, or a drop of 69 per cent.