Tanya paid £6500 for her new car. Each year its value decreased by 8%.
How much was it worth when it was one year old?
To calculate the value of the car one year later, we need to subtract 8% from the original value.
8% of £6500 is (8/100) * £6500 = £520
Therefore, the value of the car when it was one year old was £6500 - £520 = £5980. Answer: \boxed{£5980}.