Well it's worth running the argument, here's a draft representation:
Dear London Borough of Brent,
I contend the alleged contravention did not occur owing to inadequate signage. I was turning left into the road and the regulatory signs are parallel to the kerbline of Chamberlayne Road, the council obviously accept the need for an advance warning sign because one has been placed before the junction. Unfortunately it is clear that the sign before the junction has been knocked out of position, I refer you to the attached images.
In light of the above the alleged contravention did not occur, it follows that the PCN must be cancelled.
Yours faithfully,
Please send the following two images with your representation:
(https://i.imgur.com/6MduOLq.jpeg)
(https://i.imgur.com/rCUSKq7.png)
Don't forget to take a screenshot of the confirmation page.