Problem: Even after washing, this white shirt still showed ingrained grime and soiling along the collar line. Re-washing did not improve matters.

Cause: Collar grime usually consists of body oils plus atmospheric soiling including diesel fumes and carbon particles. The body oils bind the soiling onto the fabric so these must be softened with a low temperature pre-wash, below 38°C, with a little detergent. Only then can they be removed in a good main wash. Failure to soften in this way will result in them being set in the main wash. After they have been set, they become exceptionally difficult to remove as this cleaner has found.

Responsibility: The cleaner is to blame for an incorrect wash. He should ensure that the shirt washing machine has a suitable cycle that avoids this problem.