Free Traffic Legal Advice

There is no legal requirement for observation time before a PCN may be served.  Your FiL should submit reps on the basis that he had gone to get a visitor permit for the parking when the CEO served the PCN, and point out that time is always allowed to get a parking session paid for, or in his case a visitor permit, otherwise nobody could park legally.

Councils are venal and cash-strapped, and as your FiL is on the backfoot in trying to persuade them that the time taken was 'reasonable'.

IMO, just saying what you've posted is unlikely to warm them to his cause.

IMO, you'll need to consider specifics, for example:

Where the friend lives vis a vis 'os no.1 Nelson Road';

His friend did or didn't know your FiL was coming;

What evidence is there that your FiL immediately returned to his car;

If he did, did he abandon the visit or park elsewhere, possibly paying to do so of which he has a record?