@Nick325i here you go:
Dear London Borough of Brent,
I dispute liability on the ground that the alleged contravention did not occur. At the time of parking I was visiting my friend (insert full name) who resides at (insert full address and postcode).
When I parked my car I immediately went to my friend's house to obtain a visitor's permit, though I was on a single crutch that week due to hurting my Achilles during football so I wasn't as mobile as I normally would have been.
When I got to the house I was going to wait outside while she fetched a permit, so that I could speak to the CEO and explain the circumstances if I saw one approach the car, however she invited me in to get the permit which was in the kitchen.
She spent a couple of minutes rummaging through drawers before finally remembering she had left the permits by the front door, the permit was then promptly filled out and I had to return to the car on my crutch to display it (my fried could not do this as she has a newborn baby she had to tend to). Unfortunately as I got to my car I saw the CEO leaving and the PCN had already been served.
It is well established law that a motorist is allowed as long as is reasonably necessary to obtain a permit and return to their car to display it, and as long as this activity is carried out immediately and without interruption or undue delay, there is no contravention.
This must be the case because otherwise any motorist who did not have a permit already with them would be in immediate contravention the moment their vehicle became stationary, which cannot be the legal position in a road where visitors are expected to obtain a visitor's permit from the house of whoever they are visiting.
I attach a copy of the duly completed permit and I trust that in the circumstances you will agree there has been no contravention.
Yours faithfully,
Send this via https://brent.tarantoportal.com/ and keep a screenshot of the confirmation page.