Free Traffic Legal Advice

Thanks for the replies. Whats a GSV link? Also should I remove the identifying info from the PCN?  I don't do any social media so i'm quite cautious about a PCN with my car reg# and the PCN number uploaded to the internet. 

Hi everyone, I'm new to the site and would really like some help.
I'd taken my friends dog for a walk and received a ticket for apparently double parking.  I pulled up alongside their car in a residential street in Lambeth, had already messaged her to say I would be back in a couple of minutes and she was waiting at her front door.  I jumped out, opened the car door for the dog, he ran into their house.
In the meantime an ANPR car had turned into the road, one of the traffic wardens jumped out of the car and ran up to me, taking pics of my car and issued me a ticket.  I had been there for less than a minute.
I asked him why and he said I was double parked, which he said is an instant ticket.

I wasnt blocking the road since there were very few cars parked on the other side of the road so masses of space for even a truck to pass.

Was I technically parked?  Can I challenge the ticket?

Thanks in advance for any help you can give.
B