A friend has a Golf 1.9 TDi which is four years old. The Volkswagen garage she uses has advised her to have the timing belt changed based on the age of the car, not the mileage, which is not high.

Having read your Daily Telegraph column for years, I'm aware that other items such as the water pump should be changed at the same time, although the garage has not mentioned this.

Please can you tell me exactly which items she ought to have changed with the cam belt?